test: use eslint to fix var->const/let

Manually fix issues that eslint --fix couldn't do automatically.

PR-URL: https://github.com/nodejs/node/pull/10685
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Roman Reiss <me@silverwind.io>

test/addons/buffer-free-callback/test.js

@@ -5,8 +5,8 @@ const common = require('../../common');
 const binding = require(`./build/${common.buildType}/binding`);
 
 function check(size, alignment, offset) {
-  var buf = binding.alloc(size, alignment, offset);
-  var slice = buf.slice(size >>> 1);
+  let buf = binding.alloc(size, alignment, offset);
+  let slice = buf.slice(size >>> 1);
 
   buf = null;
   binding.check(slice);

test/addons/load-long-path/test.js

@@ -14,9 +14,9 @@ common.refreshTmpDir();
 // make a path that is more than 260 chars long.
 // Any given folder cannot have a name longer than 260 characters,
 // so create 10 nested folders each with 30 character long names.
-var addonDestinationDir = path.resolve(common.tmpDir);
+let addonDestinationDir = path.resolve(common.tmpDir);
 
-for (var i = 0; i < 10; i++) {
+for (let i = 0; i < 10; i++) {
   addonDestinationDir = path.join(addonDestinationDir, 'x'.repeat(30));
   fs.mkdirSync(addonDestinationDir);
 }
@@ -28,7 +28,7 @@ const addonPath = path.join(__dirname,
 const addonDestinationPath = path.join(addonDestinationDir, 'binding.node');
 
 // Copy binary to long path destination
-var contents = fs.readFileSync(addonPath);
+const contents = fs.readFileSync(addonPath);
 fs.writeFileSync(addonDestinationPath, contents);
 
 // Attempt to load at long path destination

test/addons/make-callback-recurse/test.js

@@ -65,7 +65,7 @@ assert.throws(function() {
   results.push(2);
 
   setImmediate(common.mustCall(function() {
-    for (var i = 0; i < results.length; i++) {
+    for (let i = 0; i < results.length; i++) {
       assert.strictEqual(results[i], i,
                          `verifyExecutionOrder(${arg}) results: ${results}`);
     }

test/addons/repl-domain-abort/test.js

@@ -4,27 +4,27 @@ const assert = require('assert');
 const repl = require('repl');
 const stream = require('stream');
 const path = require('path');
-var buildType = process.config.target_defaults.default_configuration;
-var buildPath = path.join(__dirname, 'build', buildType, 'binding');
+const buildType = process.config.target_defaults.default_configuration;
+let buildPath = path.join(__dirname, 'build', buildType, 'binding');
 // On Windows, escape backslashes in the path before passing it to REPL.
 if (common.isWindows)
   buildPath = buildPath.replace(/\\/g, '/');
-var cb_ran = false;
+let cb_ran = false;
 
 process.on('exit', function() {
   assert(cb_ran);
   console.log('ok');
 });
 
-var lines = [
+const lines = [
   // This line shouldn't cause an assertion error.
   'require(\'' + buildPath + '\')' +
   // Log output to double check callback ran.
   '.method(function() { console.log(\'cb_ran\'); });',
 ];
 
-var dInput = new stream.Readable();
-var dOutput = new stream.Writable();
+const dInput = new stream.Readable();
+const dOutput = new stream.Writable();
 
 dInput._read = function _read(size) {
   while (lines.length > 0 && this.push(lines.shift()));
@@ -38,7 +38,7 @@ dOutput._write = function _write(chunk, encoding, cb) {
   cb();
 };
 
-var options = {
+const options = {
   input: dInput,
   output: dOutput,
   terminal: false,

test/addons/stringbytes-external-exceed-max/test-stringbytes-external-at-max.js

@@ -14,8 +14,9 @@ if (!common.enoughTestMem) {
   return;
 }
 
+let buf;
 try {
-  var buf = Buffer.allocUnsafe(kStringMaxLength);
+  buf = Buffer.allocUnsafe(kStringMaxLength);
 } catch (e) {
   // If the exception is not due to memory confinement then rethrow it.
   if (e.message !== 'Array buffer allocation failed') throw (e);

test/addons/stringbytes-external-exceed-max/test-stringbytes-external-exceed-max-by-1-ascii.js

@@ -14,8 +14,9 @@ if (!common.enoughTestMem) {
 // v8::String::kMaxLength defined in v8.h
 const kStringMaxLength = process.binding('buffer').kStringMaxLength;
 
+let buf;
 try {
-  var buf = Buffer.allocUnsafe(kStringMaxLength + 1);
+  buf = Buffer.allocUnsafe(kStringMaxLength + 1);
 } catch (e) {
   // If the exception is not due to memory confinement then rethrow it.
   if (e.message !== 'Array buffer allocation failed') throw (e);

test/addons/stringbytes-external-exceed-max/test-stringbytes-external-exceed-max-by-1-base64.js

@@ -14,8 +14,9 @@ if (!common.enoughTestMem) {
 // v8::String::kMaxLength defined in v8.h
 const kStringMaxLength = process.binding('buffer').kStringMaxLength;
 
+let buf;
 try {
-  var buf = Buffer.allocUnsafe(kStringMaxLength + 1);
+  buf = Buffer.allocUnsafe(kStringMaxLength + 1);
 } catch (e) {
   // If the exception is not due to memory confinement then rethrow it.
   if (e.message !== 'Array buffer allocation failed') throw (e);

test/addons/stringbytes-external-exceed-max/test-stringbytes-external-exceed-max-by-1-binary.js

@@ -14,8 +14,9 @@ if (!common.enoughTestMem) {
 // v8::String::kMaxLength defined in v8.h
 const kStringMaxLength = process.binding('buffer').kStringMaxLength;
 
+let buf;
 try {
-  var buf = Buffer.allocUnsafe(kStringMaxLength + 1);
+  buf = Buffer.allocUnsafe(kStringMaxLength + 1);
 } catch (e) {
   // If the exception is not due to memory confinement then rethrow it.
   if (e.message !== 'Array buffer allocation failed') throw (e);
@@ -33,7 +34,7 @@ assert.throws(function() {
   buf.toString('latin1');
 }, /"toString\(\)" failed/);
 
-var maxString = buf.toString('latin1', 1);
+let maxString = buf.toString('latin1', 1);
 assert.strictEqual(maxString.length, kStringMaxLength);
 // Free the memory early instead of at the end of the next assignment
 maxString = undefined;

test/addons/stringbytes-external-exceed-max/test-stringbytes-external-exceed-max-by-1-hex.js

@@ -14,8 +14,9 @@ if (!common.enoughTestMem) {
 // v8::String::kMaxLength defined in v8.h
 const kStringMaxLength = process.binding('buffer').kStringMaxLength;
 
+let buf;
 try {
-  var buf = Buffer.allocUnsafe(kStringMaxLength + 1);
+  buf = Buffer.allocUnsafe(kStringMaxLength + 1);
 } catch (e) {
   // If the exception is not due to memory confinement then rethrow it.
   if (e.message !== 'Array buffer allocation failed') throw (e);

test/addons/stringbytes-external-exceed-max/test-stringbytes-external-exceed-max-by-1-utf8.js

@@ -14,8 +14,9 @@ if (!common.enoughTestMem) {
 // v8::String::kMaxLength defined in v8.h
 const kStringMaxLength = process.binding('buffer').kStringMaxLength;
 
+let buf;
 try {
-  var buf = Buffer.allocUnsafe(kStringMaxLength + 1);
+  buf = Buffer.allocUnsafe(kStringMaxLength + 1);
 } catch (e) {
   // If the exception is not due to memory confinement then rethrow it.
   if (e.message !== 'Array buffer allocation failed') throw (e);

test/addons/stringbytes-external-exceed-max/test-stringbytes-external-exceed-max-by-2.js

@@ -14,8 +14,9 @@ if (!common.enoughTestMem) {
 // v8::String::kMaxLength defined in v8.h
 const kStringMaxLength = process.binding('buffer').kStringMaxLength;
 
+let buf;
 try {
-  var buf = Buffer.allocUnsafe(kStringMaxLength + 2);
+  buf = Buffer.allocUnsafe(kStringMaxLength + 2);
 } catch (e) {
   // If the exception is not due to memory confinement then rethrow it.
   if (e.message !== 'Array buffer allocation failed') throw (e);

test/addons/stringbytes-external-exceed-max/test-stringbytes-external-exceed-max.js

@@ -14,8 +14,9 @@ if (!common.enoughTestMem) {
 // v8::String::kMaxLength defined in v8.h
 const kStringMaxLength = process.binding('buffer').kStringMaxLength;
 
+let buf;
 try {
-  var buf = Buffer.allocUnsafe(kStringMaxLength * 2 + 2);
+  buf = Buffer.allocUnsafe(kStringMaxLength * 2 + 2);
 } catch (e) {
   // If the exception is not due to memory confinement then rethrow it.
   if (e.message !== 'Array buffer allocation failed') throw (e);

test/common.js

@@ -212,7 +212,7 @@ exports.hasIPv6 = Object.keys(ifaces).some(function(name) {
  * the process aborts.
  */
 exports.childShouldThrowAndAbort = function() {
-  var testCmd = '';
+  let testCmd = '';
   if (!exports.isWindows) {
     // Do not create core files, as it can take a lot of disk space on
     // continuous testing and developers' machines

test/debugger/helper-debugger-repl.js

@@ -4,12 +4,12 @@ const assert = require('assert');
 const spawn = require('child_process').spawn;
 
 process.env.NODE_DEBUGGER_TIMEOUT = 2000;
-var port = common.PORT;
+const port = common.PORT;
 
-var child;
-var buffer = '';
-var expected = [];
-var quit;
+let child;
+let buffer = '';
+const expected = [];
+let quit;
 
 function startDebugger(scriptToDebug) {
   scriptToDebug = process.env.NODE_DEBUGGER_TEST_SCRIPT ||
@@ -34,23 +34,23 @@ function startDebugger(scriptToDebug) {
     console.log(line);
     assert.ok(expected.length > 0, 'Got unexpected line: ' + line);
 
-    var expectedLine = expected[0].lines.shift();
+    const expectedLine = expected[0].lines.shift();
     assert.ok(line.match(expectedLine) !== null, line + ' != ' + expectedLine);
 
     if (expected[0].lines.length === 0) {
-      var callback = expected[0].callback;
+      const callback = expected[0].callback;
       expected.shift();
       callback && callback();
     }
   });
 
-  var childClosed = false;
+  let childClosed = false;
   child.on('close', function(code) {
     assert(!code);
     childClosed = true;
   });
 
-  var quitCalled = false;
+  let quitCalled = false;
   quit = function() {
     if (quitCalled || childClosed) return;
     quitCalled = true;
@@ -60,7 +60,7 @@ function startDebugger(scriptToDebug) {
 
   setTimeout(function() {
     console.error('dying badly buffer=%j', buffer);
-    var err = 'Timeout';
+    let err = 'Timeout';
     if (expected.length > 0 && expected[0].lines) {
       err = err + '. Expected: ' + expected[0].lines.shift();
     }
@@ -95,7 +95,7 @@ function addTest(input, output) {
       child.stdin.write(expected[0].input + '\n');
 
       if (!expected[0].lines) {
-        var callback = expected[0].callback;
+        const callback = expected[0].callback;
         expected.shift();
 
         callback && callback();
@@ -107,17 +107,17 @@ function addTest(input, output) {
   expected.push({input: input, lines: output, callback: next});
 }
 
-var handshakeLines = [
+const handshakeLines = [
   /listening on /,
   /connecting.* ok/
 ];
 
-var initialBreakLines = [
+const initialBreakLines = [
   /break in .*:1/,
   /1/, /2/, /3/
 ];
 
-var initialLines = handshakeLines.concat(initialBreakLines);
+const initialLines = handshakeLines.concat(initialBreakLines);
 
 // Process initial lines
 addTest(null, initialLines);

test/debugger/test-debugger-repl-restart.js

@@ -3,13 +3,13 @@ require('../common');
 const repl = require('./helper-debugger-repl.js');
 
 repl.startDebugger('breakpoints.js');
-var linesWithBreakpoint = [
+const linesWithBreakpoint = [
   /1/, /2/, /3/, /4/, /5/, /\* 6/
 ];
 // We slice here, because addTest will change the given array.
 repl.addTest('sb(6)', linesWithBreakpoint.slice());
 
-var initialLines = repl.initialLines.slice();
+const initialLines = repl.initialLines.slice();
 initialLines.splice(2, 0, /Restoring/, /Warning/);
 
 // Restart the debugged script

test/debugger/test-debugger-repl-term.js

@@ -6,7 +6,7 @@ const repl = require('./helper-debugger-repl.js');
 
 repl.startDebugger('breakpoints.js');
 
-var addTest = repl.addTest;
+const addTest = repl.addTest;
 
 // next
 addTest('n', [

test/debugger/test-debugger-repl-utf8.js

@@ -1,6 +1,6 @@
 'use strict';
 const common = require('../common');
-var script = common.fixturesDir + '/breakpoints_utf8.js';
+const script = common.fixturesDir + '/breakpoints_utf8.js';
 process.env.NODE_DEBUGGER_TEST_SCRIPT = script;
 
 require('./test-debugger-repl.js');

test/debugger/test-debugger-repl.js

@@ -4,7 +4,7 @@ const repl = require('./helper-debugger-repl.js');
 
 repl.startDebugger('breakpoints.js');
 
-var addTest = repl.addTest;
+const addTest = repl.addTest;
 
 // Next
 addTest('n', [

test/gc/test-http-client-connaborted.js

@@ -18,7 +18,7 @@ let countGC = 0;
 
 console.log('We should do ' + todo + ' requests');
 
-var server = http.createServer(serverHandler);
+const server = http.createServer(serverHandler);
 server.listen(0, getall);
 
 function getall() {
@@ -31,7 +31,7 @@ function getall() {
       statusLater();
     }
 
-    var req = http.get({
+    const req = http.get({
       hostname: 'localhost',
       pathname: '/',
       port: server.address().port
@@ -44,14 +44,14 @@ function getall() {
   setImmediate(getall);
 }
 
-for (var i = 0; i < 10; i++)
+for (let i = 0; i < 10; i++)
   getall();
 
 function afterGC() {
   countGC++;
 }
 
-var timer;
+let timer;
 function statusLater() {
   global.gc();
   if (timer) clearTimeout(timer);

test/gc/test-http-client-onerror.js

@@ -20,7 +20,7 @@ let countGC = 0;
 
 console.log('We should do ' + todo + ' requests');
 
-var server = http.createServer(serverHandler);
+const server = http.createServer(serverHandler);
 server.listen(0, runTest);
 
 function getall() {
@@ -37,7 +37,7 @@ function getall() {
       throw er;
     }
 
-    var req = http.get({
+    const req = http.get({
       hostname: 'localhost',
       pathname: '/',
       port: server.address().port
@@ -51,7 +51,7 @@ function getall() {
 }
 
 function runTest() {
-  for (var i = 0; i < 10; i++)
+  for (let i = 0; i < 10; i++)
     getall();
 }
 
@@ -59,7 +59,7 @@ function afterGC() {
   countGC++;
 }
 
-var timer;
+let timer;
 function statusLater() {
   global.gc();
   if (timer) clearTimeout(timer);

test/gc/test-http-client-timeout.js

@@ -22,7 +22,7 @@ let countGC = 0;
 
 console.log('We should do ' + todo + ' requests');
 
-var server = http.createServer(serverHandler);
+const server = http.createServer(serverHandler);
 server.listen(0, getall);
 
 function getall() {
@@ -36,7 +36,7 @@ function getall() {
       statusLater();
     }
 
-    var req = http.get({
+    const req = http.get({
       hostname: 'localhost',
       pathname: '/',
       port: server.address().port
@@ -53,14 +53,14 @@ function getall() {
   setImmediate(getall);
 }
 
-for (var i = 0; i < 10; i++)
+for (let i = 0; i < 10; i++)
   getall();
 
 function afterGC() {
   countGC++;
 }
 
-var timer;
+let timer;
 function statusLater() {
   global.gc();
   if (timer) clearTimeout(timer);

test/gc/test-http-client.js

@@ -18,7 +18,7 @@ let countGC = 0;
 
 console.log('We should do ' + todo + ' requests');
 
-var server = http.createServer(serverHandler);
+const server = http.createServer(serverHandler);
 server.listen(0, getall);
 
 
@@ -34,7 +34,7 @@ function getall() {
       res.on('end', global.gc);
     }
 
-    var req = http.get({
+    const req = http.get({
       hostname: 'localhost',
       pathname: '/',
       port: server.address().port
@@ -47,7 +47,7 @@ function getall() {
   setImmediate(getall);
 }
 
-for (var i = 0; i < 10; i++)
+for (let i = 0; i < 10; i++)
   getall();
 
 function afterGC() {

test/gc/test-net-timeout.js

@@ -7,14 +7,13 @@ require('../common');
 function serverHandler(sock) {
   sock.setTimeout(120000);
   sock.resume();
-  var timer;
   sock.on('close', function() {
     clearTimeout(timer);
   });
   sock.on('error', function(err) {
     assert.strictEqual(err.code, 'ECONNRESET');
   });
-  timer = setTimeout(function() {
+  const timer = setTimeout(function() {
     sock.end('hello\n');
   }, 100);
 }
@@ -29,7 +28,7 @@ let countGC = 0;
 
 console.log('We should do ' + todo + ' requests');
 
-var server = net.createServer(serverHandler);
+const server = net.createServer(serverHandler);
 server.listen(0, getall);
 
 function getall() {
@@ -50,7 +49,7 @@ function getall() {
   setImmediate(getall);
 }
 
-for (var i = 0; i < 10; i++)
+for (let i = 0; i < 10; i++)
   getall();
 
 function afterGC() {

test/inspector/inspector-helper.js

@@ -110,7 +110,7 @@ function makeBufferingDataCallback(dataCallback) {
       buffer = Buffer.alloc(0);
     else
       buffer = Buffer.from(lines.pop(), 'utf8');
-    for (var line of lines)
+    for (const line of lines)
       dataCallback(line);
   };
 }
@@ -222,7 +222,7 @@ TestSession.prototype.sendInspectorCommands = function(commands) {
 };
 
 TestSession.prototype.createCallbackWithTimeout_ = function(message) {
-  var promise = new Promise((resolve) => {
+  const promise = new Promise((resolve) => {
     this.enqueue((callback) => {
       const timeoutId = timeout(message);
       resolve(() => {

test/internet/test-dgram-multicast-multi-process.js

@@ -13,6 +13,7 @@ const messages = [
 ];
 const workers = {};
 const listeners = 3;
+let listening, sendSocket, done, timer, dead;
 
 
 // Skip test in FreeBSD jails.
@@ -76,10 +77,10 @@ function launchChildProcess(index) {
         Object.keys(workers).forEach(function(pid) {
           const worker = workers[pid];
 
-          var count = 0;
+          let count = 0;
 
           worker.messagesReceived.forEach(function(buf) {
-            for (var i = 0; i < messages.length; ++i) {
+            for (let i = 0; i < messages.length; ++i) {
               if (buf.toString() === messages[i].toString()) {
                 count++;
                 break;
@@ -110,13 +111,13 @@ function killChildren(children) {
 }
 
 if (process.argv[2] !== 'child') {
-  var listening = 0;
-  var dead = 0;
-  var i = 0;
-  var done = 0;
+  listening = 0;
+  dead = 0;
+  let i = 0;
+  done = 0;
 
   // Exit the test if it doesn't succeed within TIMEOUT.
-  var timer = setTimeout(function() {
+  timer = setTimeout(function() {
     console.error('[PARENT] Responses were not received within %d ms.',
                   TIMEOUT);
     console.error('[PARENT] Fail');
@@ -127,11 +128,11 @@ if (process.argv[2] !== 'child') {
   }, TIMEOUT);
 
   // Launch child processes.
-  for (var x = 0; x < listeners; x++) {
+  for (let x = 0; x < listeners; x++) {
     launchChildProcess(x);
   }
 
-  var sendSocket = dgram.createSocket('udp4');
+  sendSocket = dgram.createSocket('udp4');
 
   // The socket is actually created async now.
   sendSocket.on('listening', function() {

test/internet/test-dgram-send-cb-quelches-error.js

@@ -1,12 +1,12 @@
 'use strict';
 const common = require('../common');
-var mustCall = common.mustCall;
+const mustCall = common.mustCall;
 const assert = require('assert');
 const dgram = require('dgram');
 const dns = require('dns');
 
-var socket = dgram.createSocket('udp4');
-var buffer = Buffer.from('gary busey');
+const socket = dgram.createSocket('udp4');
+const buffer = Buffer.from('gary busey');
 
 dns.setServers([]);
 

test/internet/test-dns-cares-domains.js

@@ -4,7 +4,7 @@ const assert = require('assert');
 const dns = require('dns');
 const domain = require('domain');
 
-var methods = [
+const methods = [
   'resolve4',
   'resolve6',
   'resolveCname',
@@ -18,7 +18,7 @@ var methods = [
 ];
 
 methods.forEach(function(method) {
-  var d = domain.create();
+  const d = domain.create();
   d.run(function() {
     dns[method]('google.com', function() {
       assert.strictEqual(process.domain, d, method + ' retains domain');

test/internet/test-dns.js

@@ -15,7 +15,7 @@ const queue = [];
 
 function TEST(f) {
   function next() {
-    var f = queue.shift();
+    const f = queue.shift();
     if (f) {
       running = true;
       console.log(f.name);
@@ -44,7 +44,7 @@ function checkWrap(req) {
 
 
 TEST(function test_reverse_bogus(done) {
-  var error;
+  let error;
 
   try {
     dns.reverse('bogus ip', function() {
@@ -61,12 +61,12 @@ TEST(function test_reverse_bogus(done) {
 });
 
 TEST(function test_resolve4_ttl(done) {
-  var req = dns.resolve4('google.com', { ttl: true }, function(err, result) {
+  const req = dns.resolve4('google.com', { ttl: true }, function(err, result) {
     assert.ifError(err);
     assert.ok(result.length > 0);
 
-    for (var i = 0; i < result.length; i++) {
-      var item = result[i];
+    for (let i = 0; i < result.length; i++) {
+      const item = result[i];
       assert.ok(item);
       assert.strictEqual(typeof item, 'object');
       assert.strictEqual(typeof item.ttl, 'number');
@@ -82,12 +82,12 @@ TEST(function test_resolve4_ttl(done) {
 });
 
 TEST(function test_resolve6_ttl(done) {
-  var req = dns.resolve6('google.com', { ttl: true }, function(err, result) {
+  const req = dns.resolve6('google.com', { ttl: true }, function(err, result) {
     assert.ifError(err);
     assert.ok(result.length > 0);
 
-    for (var i = 0; i < result.length; i++) {
-      var item = result[i];
+    for (let i = 0; i < result.length; i++) {
+      const item = result[i];
       assert.ok(item);
       assert.strictEqual(typeof item, 'object');
       assert.strictEqual(typeof item.ttl, 'number');
@@ -103,12 +103,12 @@ TEST(function test_resolve6_ttl(done) {
 });
 
 TEST(function test_resolveMx(done) {
-  var req = dns.resolveMx('gmail.com', function(err, result) {
+  const req = dns.resolveMx('gmail.com', function(err, result) {
     assert.ifError(err);
     assert.ok(result.length > 0);
 
-    for (var i = 0; i < result.length; i++) {
-      var item = result[i];
+    for (let i = 0; i < result.length; i++) {
+      const item = result[i];
       assert.ok(item);
       assert.strictEqual(typeof item, 'object');
 
@@ -125,7 +125,7 @@ TEST(function test_resolveMx(done) {
 });
 
 TEST(function test_resolveMx_failure(done) {
-  var req = dns.resolveMx('something.invalid', function(err, result) {
+  const req = dns.resolveMx('something.invalid', function(err, result) {
     assert.ok(err instanceof Error);
     assert.strictEqual(err.errno, 'ENOTFOUND');
 
@@ -138,12 +138,12 @@ TEST(function test_resolveMx_failure(done) {
 });
 
 TEST(function test_resolveNs(done) {
-  var req = dns.resolveNs('rackspace.com', function(err, names) {
+  const req = dns.resolveNs('rackspace.com', function(err, names) {
     assert.ifError(err);
     assert.ok(names.length > 0);
 
-    for (var i = 0; i < names.length; i++) {
-      var name = names[i];
+    for (let i = 0; i < names.length; i++) {
+      const name = names[i];
       assert.ok(name);
       assert.strictEqual(typeof name, 'string');
     }
@@ -155,7 +155,7 @@ TEST(function test_resolveNs(done) {
 });
 
 TEST(function test_resolveNs_failure(done) {
-  var req = dns.resolveNs('something.invalid', function(err, result) {
+  const req = dns.resolveNs('something.invalid', function(err, result) {
     assert.ok(err instanceof Error);
     assert.strictEqual(err.errno, 'ENOTFOUND');
 
@@ -168,12 +168,12 @@ TEST(function test_resolveNs_failure(done) {
 });
 
 TEST(function test_resolveSrv(done) {
-  var req = dns.resolveSrv('_jabber._tcp.google.com', function(err, result) {
+  const req = dns.resolveSrv('_jabber._tcp.google.com', function(err, result) {
     assert.ifError(err);
     assert.ok(result.length > 0);
 
-    for (var i = 0; i < result.length; i++) {
-      var item = result[i];
+    for (let i = 0; i < result.length; i++) {
+      const item = result[i];
       assert.ok(item);
       assert.strictEqual(typeof item, 'object');
 
@@ -192,7 +192,7 @@ TEST(function test_resolveSrv(done) {
 });
 
 TEST(function test_resolveSrv_failure(done) {
-  var req = dns.resolveSrv('something.invalid', function(err, result) {
+  const req = dns.resolveSrv('something.invalid', function(err, result) {
     assert.ok(err instanceof Error);
     assert.strictEqual(err.errno, 'ENOTFOUND');
 
@@ -205,12 +205,12 @@ TEST(function test_resolveSrv_failure(done) {
 });
 
 TEST(function test_resolvePtr(done) {
-  var req = dns.resolvePtr('8.8.8.8.in-addr.arpa', function(err, result) {
+  const req = dns.resolvePtr('8.8.8.8.in-addr.arpa', function(err, result) {
     assert.ifError(err);
     assert.ok(result.length > 0);
 
-    for (var i = 0; i < result.length; i++) {
-      var item = result[i];
+    for (let i = 0; i < result.length; i++) {
+      const item = result[i];
       assert.ok(item);
       assert.strictEqual(typeof item, 'string');
     }
@@ -222,7 +222,7 @@ TEST(function test_resolvePtr(done) {
 });
 
 TEST(function test_resolvePtr_failure(done) {
-  var req = dns.resolvePtr('something.invalid', function(err, result) {
+  const req = dns.resolvePtr('something.invalid', function(err, result) {
     assert.ok(err instanceof Error);
     assert.strictEqual(err.errno, 'ENOTFOUND');
 
@@ -235,12 +235,12 @@ TEST(function test_resolvePtr_failure(done) {
 });
 
 TEST(function test_resolveNaptr(done) {
-  var req = dns.resolveNaptr('sip2sip.info', function(err, result) {
+  const req = dns.resolveNaptr('sip2sip.info', function(err, result) {
     assert.ifError(err);
     assert.ok(result.length > 0);
 
-    for (var i = 0; i < result.length; i++) {
-      var item = result[i];
+    for (let i = 0; i < result.length; i++) {
+      const item = result[i];
       assert.ok(item);
       assert.strictEqual(typeof item, 'object');
 
@@ -259,7 +259,7 @@ TEST(function test_resolveNaptr(done) {
 });
 
 TEST(function test_resolveNaptr_failure(done) {
-  var req = dns.resolveNaptr('something.invalid', function(err, result) {
+  const req = dns.resolveNaptr('something.invalid', function(err, result) {
     assert.ok(err instanceof Error);
     assert.strictEqual(err.errno, 'ENOTFOUND');
 
@@ -272,7 +272,7 @@ TEST(function test_resolveNaptr_failure(done) {
 });
 
 TEST(function test_resolveSoa(done) {
-  var req = dns.resolveSoa('nodejs.org', function(err, result) {
+  const req = dns.resolveSoa('nodejs.org', function(err, result) {
     assert.ifError(err);
     assert.ok(result);
     assert.strictEqual(typeof result, 'object');
@@ -305,7 +305,7 @@ TEST(function test_resolveSoa(done) {
 });
 
 TEST(function test_resolveSoa_failure(done) {
-  var req = dns.resolveSoa('something.invalid', function(err, result) {
+  const req = dns.resolveSoa('something.invalid', function(err, result) {
     assert.ok(err instanceof Error);
     assert.strictEqual(err.errno, 'ENOTFOUND');
 
@@ -318,12 +318,12 @@ TEST(function test_resolveSoa_failure(done) {
 });
 
 TEST(function test_resolveCname(done) {
-  var req = dns.resolveCname('www.microsoft.com', function(err, names) {
+  const req = dns.resolveCname('www.microsoft.com', function(err, names) {
     assert.ifError(err);
     assert.ok(names.length > 0);
 
-    for (var i = 0; i < names.length; i++) {
-      var name = names[i];
+    for (let i = 0; i < names.length; i++) {
+      const name = names[i];
       assert.ok(name);
       assert.strictEqual(typeof name, 'string');
     }
@@ -335,7 +335,7 @@ TEST(function test_resolveCname(done) {
 });
 
 TEST(function test_resolveCname_failure(done) {
-  var req = dns.resolveCname('something.invalid', function(err, result) {
+  const req = dns.resolveCname('something.invalid', function(err, result) {
     assert.ok(err instanceof Error);
     assert.strictEqual(err.errno, 'ENOTFOUND');
 
@@ -349,7 +349,7 @@ TEST(function test_resolveCname_failure(done) {
 
 
 TEST(function test_resolveTxt(done) {
-  var req = dns.resolveTxt('google.com', function(err, records) {
+  const req = dns.resolveTxt('google.com', function(err, records) {
     assert.ifError(err);
     assert.strictEqual(records.length, 1);
     assert.ok(util.isArray(records[0]));
@@ -361,7 +361,7 @@ TEST(function test_resolveTxt(done) {
 });
 
 TEST(function test_resolveTxt_failure(done) {
-  var req = dns.resolveTxt('something.invalid', function(err, result) {
+  const req = dns.resolveTxt('something.invalid', function(err, result) {
     assert.ok(err instanceof Error);
     assert.strictEqual(err.errno, 'ENOTFOUND');
 
@@ -375,7 +375,7 @@ TEST(function test_resolveTxt_failure(done) {
 
 
 TEST(function test_lookup_failure(done) {
-  var req = dns.lookup('does.not.exist', 4, function(err, ip, family) {
+  const req = dns.lookup('does.not.exist', 4, function(err, ip, family) {
     assert.ok(err instanceof Error);
     assert.strictEqual(err.errno, dns.NOTFOUND);
     assert.strictEqual(err.errno, 'ENOTFOUND');
@@ -390,7 +390,7 @@ TEST(function test_lookup_failure(done) {
 
 
 TEST(function test_lookup_null(done) {
-  var req = dns.lookup(null, function(err, ip, family) {
+  const req = dns.lookup(null, function(err, ip, family) {
     assert.ifError(err);
     assert.strictEqual(ip, null);
     assert.strictEqual(family, 4);
@@ -403,7 +403,7 @@ TEST(function test_lookup_null(done) {
 
 
 TEST(function test_lookup_ip_all(done) {
-  var req = dns.lookup('127.0.0.1', {all: true}, function(err, ips, family) {
+  const req = dns.lookup('127.0.0.1', {all: true}, function(err, ips, family) {
     assert.ifError(err);
     assert.ok(Array.isArray(ips));
     assert.ok(ips.length > 0);
@@ -418,7 +418,7 @@ TEST(function test_lookup_ip_all(done) {
 
 
 TEST(function test_lookup_null_all(done) {
-  var req = dns.lookup(null, {all: true}, function(err, ips, family) {
+  const req = dns.lookup(null, {all: true}, function(err, ips, family) {
     assert.ifError(err);
     assert.ok(Array.isArray(ips));
     assert.strictEqual(ips.length, 0);
@@ -431,7 +431,7 @@ TEST(function test_lookup_null_all(done) {
 
 
 TEST(function test_lookup_all_mixed(done) {
-  var req = dns.lookup('www.google.com', {all: true}, function(err, ips) {
+  const req = dns.lookup('www.google.com', {all: true}, function(err, ips) {
     assert.ifError(err);
     assert.ok(Array.isArray(ips));
     assert.ok(ips.length > 0);
@@ -453,7 +453,7 @@ TEST(function test_lookup_all_mixed(done) {
 
 
 TEST(function test_lookupservice_invalid(done) {
-  var req = dns.lookupService('1.2.3.4', 80, function(err, host, service) {
+  const req = dns.lookupService('1.2.3.4', 80, function(err, host, service) {
     assert(err instanceof Error);
     assert.strictEqual(err.code, 'ENOTFOUND');
     assert.ok(/1\.2\.3\.4/.test(err.message));
@@ -466,7 +466,7 @@ TEST(function test_lookupservice_invalid(done) {
 
 
 TEST(function test_reverse_failure(done) {
-  var req = dns.reverse('0.0.0.0', function(err) {
+  const req = dns.reverse('0.0.0.0', function(err) {
     assert(err instanceof Error);
     assert.strictEqual(err.code, 'ENOTFOUND');  // Silly error code...
     assert.strictEqual(err.hostname, '0.0.0.0');
@@ -480,7 +480,7 @@ TEST(function test_reverse_failure(done) {
 
 
 TEST(function test_lookup_failure(done) {
-  var req = dns.lookup('nosuchhostimsure', function(err) {
+  const req = dns.lookup('nosuchhostimsure', function(err) {
     assert(err instanceof Error);
     assert.strictEqual(err.code, 'ENOTFOUND');  // Silly error code...
     assert.strictEqual(err.hostname, 'nosuchhostimsure');
@@ -494,7 +494,7 @@ TEST(function test_lookup_failure(done) {
 
 
 TEST(function test_resolve_failure(done) {
-  var req = dns.resolve4('nosuchhostimsure', function(err) {
+  const req = dns.resolve4('nosuchhostimsure', function(err) {
     assert(err instanceof Error);
 
     switch (err.code) {
@@ -516,12 +516,12 @@ TEST(function test_resolve_failure(done) {
 });
 
 
-var getaddrinfoCallbackCalled = false;
+let getaddrinfoCallbackCalled = false;
 
 console.log('looking up nodejs.org...');
 
-var cares = process.binding('cares_wrap');
-var req = new cares.GetAddrInfoReqWrap();
+const cares = process.binding('cares_wrap');
+const req = new cares.GetAddrInfoReqWrap();
 cares.getaddrinfo(req, 'nodejs.org', 4);
 
 req.oncomplete = function(err, domains) {

test/internet/test-net-connect-timeout.js

@@ -7,21 +7,21 @@ const common = require('../common');
 const net = require('net');
 const assert = require('assert');
 
-var start = new Date();
+const start = new Date();
 
-var T = 100;
+const T = 100;
 
 // 192.0.2.1 is part of subnet assigned as "TEST-NET" in RFC 5737.
 // For use solely in documentation and example source code.
 // In short, it should be unreachable.
 // In practice, it's a network black hole.
-var socket = net.createConnection(9999, '192.0.2.1');
+const socket = net.createConnection(9999, '192.0.2.1');
 
 socket.setTimeout(T);
 
 socket.on('timeout', common.mustCall(function() {
   console.error('timeout');
-  var now = new Date();
+  const now = new Date();
   assert.ok(now - start < T + 500);
   socket.destroy();
 }));

test/internet/test-net-connect-unref.js

@@ -2,10 +2,9 @@
 const common = require('../common');
 const net = require('net');
 
-var client;
-var TIMEOUT = 10 * 1000;
+const TIMEOUT = 10 * 1000;
 
-client = net.createConnection(53, '8.8.8.8', function() {
+const client = net.createConnection(53, '8.8.8.8', function() {
   client.unref();
 });
 

test/internet/test-tls-connnect-melissadata.js

@@ -9,7 +9,7 @@ if (!common.hasCrypto) {
 }
 
 const tls = require('tls');
-var socket = tls.connect(443, 'address.melissadata.net', function() {
+const socket = tls.connect(443, 'address.melissadata.net', function() {
   socket.resume();
   socket.destroy();
 });

test/known_issues/test-url-parse-conformance.js

@@ -9,14 +9,14 @@ const path = require('path');
 
 const tests = require(path.join(common.fixturesDir, 'url-tests.json'));
 
-var failed = 0;
-var attempted = 0;
+let failed = 0;
+let attempted = 0;
 
 tests.forEach((test) => {
   attempted++;
   // Skip comments
   if (typeof test === 'string') return;
-  var parsed;
+  let parsed;
 
   try {
     // Attempt to parse
@@ -28,7 +28,7 @@ tests.forEach((test) => {
     } else {
       // Test was not supposed to fail, so we're good so far. Now
       // check the results of the parse.
-      var username, password;
+      let username, password;
       try {
         assert.strictEqual(test.href, parsed.href);
         assert.strictEqual(test.protocol, parsed.protocol);

test/message/eval_messages.js

@@ -5,16 +5,16 @@ require('../common');
 const spawn = require('child_process').spawn;
 
 function run(cmd, strict, cb) {
-  var args = [];
+  const args = [];
   if (strict) args.push('--use_strict');
   args.push('-pe', cmd);
-  var child = spawn(process.execPath, args);
+  const child = spawn(process.execPath, args);
   child.stdout.pipe(process.stdout);
   child.stderr.pipe(process.stdout);
   child.on('close', cb);
 }
 
-var queue =
+const queue =
   [ 'with(this){__filename}',
     '42',
     'throw new Error("hello")',
@@ -22,7 +22,7 @@ var queue =
     'var ______________________________________________; throw 10' ];
 
 function go() {
-  var c = queue.shift();
+  const c = queue.shift();
   if (!c) return console.log('done');
   run(c, false, function() {
     run(c, true, go);

test/message/max_tick_depth.js

@@ -2,7 +2,7 @@
 require('../common');
 
 process.maxTickDepth = 10;
-var i = 20;
+let i = 20;
 process.nextTick(function f() {
   console.error('tick %d', i);
   if (i-- > 0)

test/message/stdin_messages.js

@@ -5,17 +5,17 @@ require('../common');
 const spawn = require('child_process').spawn;
 
 function run(cmd, strict, cb) {
-  var args = [];
+  const args = [];
   if (strict) args.push('--use_strict');
   args.push('-p');
-  var child = spawn(process.execPath, args);
+  const child = spawn(process.execPath, args);
   child.stdout.pipe(process.stdout);
   child.stderr.pipe(process.stdout);
   child.stdin.end(cmd);
   child.on('close', cb);
 }
 
-var queue =
+const queue =
   [ 'with(this){__filename}',
     '42',
     'throw new Error("hello")',
@@ -23,7 +23,7 @@ var queue =
     'var ______________________________________________; throw 10' ];
 
 function go() {
-  var c = queue.shift();
+  const c = queue.shift();
   if (!c) return console.log('done');
   run(c, false, function() {
     run(c, true, go);

test/parallel/test-assert-typedarray-deepequal.js

@@ -5,7 +5,7 @@ const assert = require('assert');
 const a = require('assert');
 
 function makeBlock(f) {
-  var args = Array.prototype.slice.call(arguments, 1);
+  const args = Array.prototype.slice.call(arguments, 1);
   return function() {
     return f.apply(this, args);
   };

test/parallel/test-assert.js

@@ -4,7 +4,7 @@ const assert = require('assert');
 const a = require('assert');
 
 function makeBlock(f) {
-  var args = Array.prototype.slice.call(arguments, 1);
+  const args = Array.prototype.slice.call(arguments, 1);
   return function() {
     return f.apply(this, args);
   };
@@ -120,8 +120,8 @@ assert.throws(makeBlock(a.deepEqual, {a: 4}, {a: 4, b: true}),
 assert.doesNotThrow(makeBlock(a.deepEqual, ['a'], {0: 'a'}));
 //(although not necessarily the same order),
 assert.doesNotThrow(makeBlock(a.deepEqual, {a: 4, b: '1'}, {b: '1', a: 4}));
-var a1 = [1, 2, 3];
-var a2 = [1, 2, 3];
+const a1 = [1, 2, 3];
+const a2 = [1, 2, 3];
 a1.a = 'test';
 a1.b = true;
 a2.b = true;
@@ -131,7 +131,7 @@ assert.throws(makeBlock(a.deepEqual, Object.keys(a1), Object.keys(a2)),
 assert.doesNotThrow(makeBlock(a.deepEqual, a1, a2));
 
 // having an identical prototype property
-var nbRoot = {
+const nbRoot = {
   toString: function() { return this.first + ' ' + this.last; }
 };
 
@@ -149,8 +149,8 @@ function nameBuilder2(first, last) {
 }
 nameBuilder2.prototype = nbRoot;
 
-var nb1 = new nameBuilder('Ryan', 'Dahl');
-var nb2 = new nameBuilder2('Ryan', 'Dahl');
+const nb1 = new nameBuilder('Ryan', 'Dahl');
+let nb2 = new nameBuilder2('Ryan', 'Dahl');
 
 assert.doesNotThrow(makeBlock(a.deepEqual, nb1, nb2));
 
@@ -267,8 +267,8 @@ function Constructor2(first, last) {
   this.last = last;
 }
 
-var obj1 = new Constructor1('Ryan', 'Dahl');
-var obj2 = new Constructor2('Ryan', 'Dahl');
+const obj1 = new Constructor1('Ryan', 'Dahl');
+let obj2 = new Constructor2('Ryan', 'Dahl');
 
 assert.throws(makeBlock(a.deepStrictEqual, obj1, obj2), a.AssertionError);
 
@@ -285,7 +285,7 @@ assert.throws(makeBlock(assert.deepStrictEqual, true, 1),
 assert.throws(makeBlock(assert.deepStrictEqual, Symbol(), Symbol()),
               a.AssertionError);
 
-var s = Symbol();
+const s = Symbol();
 assert.doesNotThrow(makeBlock(assert.deepStrictEqual, s, s));
 
 
@@ -326,7 +326,7 @@ assert.throws(makeBlock(thrower, a.AssertionError));
 assert.throws(makeBlock(thrower, TypeError));
 
 // when passing a type, only catch errors of the appropriate type
-var threw = false;
+let threw = false;
 try {
   a.throws(makeBlock(thrower, TypeError), a.AssertionError);
 } catch (e) {
@@ -394,10 +394,11 @@ a.throws(makeBlock(thrower, TypeError), function(err) {
 // https://github.com/nodejs/node/issues/3188
 threw = false;
 
+let AnotherErrorType;
 try {
-  var ES6Error = class extends Error {};
+  const ES6Error = class extends Error {};
 
-  var AnotherErrorType = class extends Error {};
+  AnotherErrorType = class extends Error {};
 
   const functionThatThrows = function() {
     throw new AnotherErrorType('foo');
@@ -436,7 +437,7 @@ assert.ok(threw);
   a.throws(makeBlock(a.deepStrictEqual, d, e), /AssertionError/);
 }
 // GH-7178. Ensure reflexivity of deepEqual with `arguments` objects.
-var args = (function() { return arguments; })();
+const args = (function() { return arguments; })();
 a.throws(makeBlock(a.deepEqual, [], args));
 a.throws(makeBlock(a.deepEqual, args, []));
 
@@ -455,7 +456,7 @@ a.throws(makeBlock(a.deepEqual, args, []));
   a.doesNotThrow(makeBlock(a.deepEqual, someArgs, sameArgs));
 }
 
-var circular = {y: 1};
+const circular = {y: 1};
 circular.x = circular;
 
 function testAssertionMessage(actual, expected) {
@@ -520,7 +521,7 @@ try {
 
 // Verify that throws() and doesNotThrow() throw on non-function block
 function testBlockTypeError(method, block) {
-  var threw = true;
+  let threw = true;
 
   try {
     method(block);

test/parallel/test-async-wrap-check-providers.js

@@ -28,7 +28,7 @@ keyList.splice(0, 1);
 // want to improve under https://github.com/nodejs/node/issues/5085.
 // strip out fs watch related parts for now
 if (common.isAix) {
-  for (var i = 0; i < keyList.length; i++) {
+  for (let i = 0; i < keyList.length; i++) {
     if ((keyList[i] === 'FSEVENTWRAP') || (keyList[i] === 'STATWATCHER')) {
       keyList.splice(i, 1);
     }

test/parallel/test-async-wrap-throw-from-callback.js

@@ -13,8 +13,8 @@ const domain = require('domain');
 const spawn = require('child_process').spawn;
 const callbacks = [ 'init', 'pre', 'post', 'destroy' ];
 const toCall = process.argv[2];
-var msgCalled = 0;
-var msgReceived = 0;
+let msgCalled = 0;
+let msgReceived = 0;
 
 function init() {
   if (toCall === 'init')
@@ -57,7 +57,7 @@ if (typeof process.argv[2] === 'string') {
     msgCalled++;
 
     const child = spawn(process.execPath, [__filename, item]);
-    var errstring = '';
+    let errstring = '';
 
     child.stderr.on('data', (data) => {
       errstring += data.toString();

test/parallel/test-async-wrap-uid.js

@@ -6,7 +6,7 @@ const assert = require('assert');
 const async_wrap = process.binding('async_wrap');
 
 // Give the event loop time to clear out the final uv_close().
-var si_cntr = 3;
+let si_cntr = 3;
 process.on('beforeExit', () => {
   if (--si_cntr > 0) setImmediate(() => {});
 });

test/parallel/test-buffer-ascii.js

@@ -16,7 +16,7 @@ const expected = 'Cb\u0000\u0019est, graphiquement, la rC)union ' +
 
 const buf = Buffer.from(input);
 
-for (var i = 0; i < expected.length; ++i) {
+for (let i = 0; i < expected.length; ++i) {
   assert.strictEqual(buf.slice(i).toString('ascii'), expected.slice(i));
 
   // Skip remainder of multi-byte sequence.

test/parallel/test-buffer-bytelength.js

@@ -24,37 +24,37 @@ assert(ArrayBuffer.isView(Buffer.allocUnsafeSlow(10)));
 assert(ArrayBuffer.isView(Buffer.from('')));
 
 // buffer
-var incomplete = Buffer.from([0xe4, 0xb8, 0xad, 0xe6, 0x96]);
+const incomplete = Buffer.from([0xe4, 0xb8, 0xad, 0xe6, 0x96]);
 assert.strictEqual(Buffer.byteLength(incomplete), 5);
-var ascii = Buffer.from('abc');
+const ascii = Buffer.from('abc');
 assert.strictEqual(Buffer.byteLength(ascii), 3);
 
 // ArrayBuffer
-var buffer = new ArrayBuffer(8);
+const buffer = new ArrayBuffer(8);
 assert.strictEqual(Buffer.byteLength(buffer), 8);
 
 // TypedArray
-var int8 = new Int8Array(8);
+const int8 = new Int8Array(8);
 assert.strictEqual(Buffer.byteLength(int8), 8);
-var uint8 = new Uint8Array(8);
+const uint8 = new Uint8Array(8);
 assert.strictEqual(Buffer.byteLength(uint8), 8);
-var uintc8 = new Uint8ClampedArray(2);
+const uintc8 = new Uint8ClampedArray(2);
 assert.strictEqual(Buffer.byteLength(uintc8), 2);
-var int16 = new Int16Array(8);
+const int16 = new Int16Array(8);
 assert.strictEqual(Buffer.byteLength(int16), 16);
-var uint16 = new Uint16Array(8);
+const uint16 = new Uint16Array(8);
 assert.strictEqual(Buffer.byteLength(uint16), 16);
-var int32 = new Int32Array(8);
+const int32 = new Int32Array(8);
 assert.strictEqual(Buffer.byteLength(int32), 32);
-var uint32 = new Uint32Array(8);
+const uint32 = new Uint32Array(8);
 assert.strictEqual(Buffer.byteLength(uint32), 32);
-var float32 = new Float32Array(8);
+const float32 = new Float32Array(8);
 assert.strictEqual(Buffer.byteLength(float32), 32);
-var float64 = new Float64Array(8);
+const float64 = new Float64Array(8);
 assert.strictEqual(Buffer.byteLength(float64), 64);
 
 // DataView
-var dv = new DataView(new ArrayBuffer(2));
+const dv = new DataView(new ArrayBuffer(2));
 assert.strictEqual(Buffer.byteLength(dv), 2);
 
 // special case: zero length string

test/parallel/test-buffer-concat.js

@@ -5,7 +5,7 @@ const assert = require('assert');
 const zero = [];
 const one = [ Buffer.from('asdf') ];
 const long = [];
-for (var i = 0; i < 10; i++) long.push(Buffer.from('asdf'));
+for (let i = 0; i < 10; i++) long.push(Buffer.from('asdf'));
 
 const flatZero = Buffer.concat(zero);
 const flatOne = Buffer.concat(one);

test/parallel/test-buffer-copy.js

@@ -5,7 +5,7 @@ const assert = require('assert');
 
 const b = Buffer.allocUnsafe(1024);
 const c = Buffer.allocUnsafe(512);
-var cntr = 0;
+let cntr = 0;
 
 {
   // copy 512 bytes, from 0 to 512.

test/parallel/test-buffer-fill.js

@@ -243,7 +243,7 @@ function writeToFill(string, offset, end, encoding) {
   // Convert "end" to "length" (which write understands).
   const length = end - offset < 0 ? 0 : end - offset;
 
-  var wasZero = false;
+  let wasZero = false;
   do {
     const written = buf2.write(string, offset, length, encoding);
     offset += written;
@@ -324,7 +324,7 @@ Buffer.alloc(8, '');
 {
   let elseWasLast = false;
   assert.throws(() => {
-    var ctr = 0;
+    let ctr = 0;
     const start = {
       [Symbol.toPrimitive]() {
         // We use this condition to get around the check in lib/buffer.js
@@ -357,7 +357,7 @@ assert.throws(() => {
 {
   let elseWasLast = false;
   assert.throws(() => {
-    var ctr = 0;
+    let ctr = 0;
     const end = {
       [Symbol.toPrimitive]() {
         // We use this condition to get around the check in lib/buffer.js

test/parallel/test-buffer-includes.js

@@ -140,7 +140,7 @@ assert.strictEqual(
 
 
 // test usc2 encoding
-var twoByteString = Buffer.from('\u039a\u0391\u03a3\u03a3\u0395', 'ucs2');
+let twoByteString = Buffer.from('\u039a\u0391\u03a3\u03a3\u0395', 'ucs2');
 
 assert(twoByteString.includes('\u0395', 4, 'ucs2'));
 assert(twoByteString.includes('\u03a3', -4, 'ucs2'));
@@ -190,7 +190,7 @@ assert(!mixedByteStringUtf8.includes('\u0396'));
 
 // Test complex string includes algorithms. Only trigger for long strings.
 // Long string that isn't a simple repeat of a shorter string.
-var longString = 'A';
+let longString = 'A';
 for (let i = 66; i < 76; i++) {  // from 'B' to 'K'
   longString = longString + String.fromCharCode(i) + longString;
 }
@@ -198,7 +198,7 @@ for (let i = 66; i < 76; i++) {  // from 'B' to 'K'
 const longBufferString = Buffer.from(longString);
 
 // pattern of 15 chars, repeated every 16 chars in long
-var pattern = 'ABACABADABACABA';
+let pattern = 'ABACABADABACABA';
 for (let i = 0; i < longBufferString.length - pattern.length; i += 7) {
   const includes = longBufferString.includes(pattern, i);
   assert(includes, 'Long ABACABA...-string at index ' + i);
@@ -229,8 +229,8 @@ assert(!allCharsBufferUtf8.includes('notfound'));
 assert(!allCharsBufferUcs2.includes('notfound'));
 
 // Find substrings in Utf8.
-var lengths = [1, 3, 15];  // Single char, simple and complex.
-var indices = [0x5, 0x60, 0x400, 0x680, 0x7ee, 0xFF02, 0x16610, 0x2f77b];
+let lengths = [1, 3, 15];  // Single char, simple and complex.
+let indices = [0x5, 0x60, 0x400, 0x680, 0x7ee, 0xFF02, 0x16610, 0x2f77b];
 for (let lengthIndex = 0; lengthIndex < lengths.length; lengthIndex++) {
   for (let i = 0; i < indices.length; i++) {
     const index = indices[i];

test/parallel/test-buffer-indexof.js

@@ -191,7 +191,7 @@ assert.equal(Buffer.from('aaaa00a').indexOf('3030', 'hex'), 4);
   assert.equal(-1, twoByteString.indexOf('\u03a3', -2, 'ucs2'));
 }
 
-var mixedByteStringUcs2 =
+const mixedByteStringUcs2 =
     Buffer.from('\u039a\u0391abc\u03a3\u03a3\u0395', 'ucs2');
 assert.equal(6, mixedByteStringUcs2.indexOf('bc', 0, 'ucs2'));
 assert.equal(10, mixedByteStringUcs2.indexOf('\u03a3', 0, 'ucs2'));
@@ -226,7 +226,7 @@ assert.equal(
       6, twoByteString.indexOf('\u03a3\u0395', 0, 'ucs2'), 'Sigma Epsilon');
 }
 
-var mixedByteStringUtf8 = Buffer.from('\u039a\u0391abc\u03a3\u03a3\u0395');
+const mixedByteStringUtf8 = Buffer.from('\u039a\u0391abc\u03a3\u03a3\u0395');
 assert.equal(5, mixedByteStringUtf8.indexOf('bc'));
 assert.equal(5, mixedByteStringUtf8.indexOf('bc', 5));
 assert.equal(5, mixedByteStringUtf8.indexOf('bc', -8));
@@ -236,15 +236,15 @@ assert.equal(-1, mixedByteStringUtf8.indexOf('\u0396'));
 
 // Test complex string indexOf algorithms. Only trigger for long strings.
 // Long string that isn't a simple repeat of a shorter string.
-var longString = 'A';
+let longString = 'A';
 for (let i = 66; i < 76; i++) {  // from 'B' to 'K'
   longString = longString + String.fromCharCode(i) + longString;
 }
 
-var longBufferString = Buffer.from(longString);
+const longBufferString = Buffer.from(longString);
 
 // pattern of 15 chars, repeated every 16 chars in long
-var pattern = 'ABACABADABACABA';
+let pattern = 'ABACABADABACABA';
 for (let i = 0; i < longBufferString.length - pattern.length; i += 7) {
   const index = longBufferString.indexOf(pattern, i);
   assert.equal((i + 15) & ~0xf, index, 'Long ABACABA...-string at index ' + i);
@@ -260,17 +260,17 @@ assert.equal(
     1535, longBufferString.indexOf(pattern, 512), 'Long JABACABA..., Second J');
 
 // Search for a non-ASCII string in a pure ASCII string.
-var asciiString = Buffer.from(
+const asciiString = Buffer.from(
     'arglebargleglopglyfarglebargleglopglyfarglebargleglopglyf');
 assert.equal(-1, asciiString.indexOf('\x2061'));
 assert.equal(3, asciiString.indexOf('leb', 0));
 
 // Search in string containing many non-ASCII chars.
-var allCodePoints = [];
+const allCodePoints = [];
 for (let i = 0; i < 65536; i++) allCodePoints[i] = i;
-var allCharsString = String.fromCharCode.apply(String, allCodePoints);
-var allCharsBufferUtf8 = Buffer.from(allCharsString);
-var allCharsBufferUcs2 = Buffer.from(allCharsString, 'ucs2');
+const allCharsString = String.fromCharCode.apply(String, allCodePoints);
+const allCharsBufferUtf8 = Buffer.from(allCharsString);
+const allCharsBufferUcs2 = Buffer.from(allCharsString, 'ucs2');
 
 // Search for string long enough to trigger complex search with ASCII pattern
 // and UC16 subject.
@@ -307,10 +307,10 @@ assert.strictEqual(Buffer.from('aaaaa').indexOf('b', 'ucs2'), -1);
         length = 4 * length;
       }
 
-      var patternBufferUtf8 = allCharsBufferUtf8.slice(index, index + length);
+      const patternBufferUtf8 = allCharsBufferUtf8.slice(index, index + length);
       assert.equal(index, allCharsBufferUtf8.indexOf(patternBufferUtf8));
 
-      var patternStringUtf8 = patternBufferUtf8.toString();
+      const patternStringUtf8 = patternBufferUtf8.toString();
       assert.equal(index, allCharsBufferUtf8.indexOf(patternStringUtf8));
     }
   }
@@ -325,12 +325,12 @@ assert.strictEqual(Buffer.from('aaaaa').indexOf('b', 'ucs2'), -1);
       const index = indices[i] * 2;
       const length = lengths[lengthIndex];
 
-      var patternBufferUcs2 =
+      const patternBufferUcs2 =
           allCharsBufferUcs2.slice(index, index + length);
       assert.equal(
           index, allCharsBufferUcs2.indexOf(patternBufferUcs2, 0, 'ucs2'));
 
-      var patternStringUcs2 = patternBufferUcs2.toString('ucs2');
+      const patternStringUcs2 = patternBufferUcs2.toString('ucs2');
       assert.equal(
           index, allCharsBufferUcs2.indexOf(patternStringUcs2, 0, 'ucs2'));
     }
@@ -434,7 +434,7 @@ assert.strictEqual(buf_bc.lastIndexOf('你好', 5, 'binary'), -1);
 assert.strictEqual(buf_bc.lastIndexOf(Buffer.from('你好'), 7), -1);
 
 // Test lastIndexOf on a longer buffer:
-var bufferString = new Buffer('a man a plan a canal panama');
+const bufferString = new Buffer('a man a plan a canal panama');
 assert.equal(15, bufferString.lastIndexOf('canal'));
 assert.equal(21, bufferString.lastIndexOf('panama'));
 assert.equal(0, bufferString.lastIndexOf('a man a plan a canal panama'));
@@ -485,16 +485,17 @@ assert.equal(511, longBufferString.lastIndexOf(pattern, 1534));
 
 // countBits returns the number of bits in the binary reprsentation of n.
 function countBits(n) {
-  for (var count = 0; n > 0; count++) {
+  let count;
+  for (count = 0; n > 0; count++) {
     n = n & (n - 1); // remove top bit
   }
   return count;
 }
-var parts = [];
-for (var i = 0; i < 1000000; i++) {
+const parts = [];
+for (let i = 0; i < 1000000; i++) {
   parts.push((countBits(i) % 2 === 0) ? 'yolo' : 'swag');
 }
-var reallyLong = new Buffer(parts.join(' '));
+const reallyLong = new Buffer(parts.join(' '));
 assert.equal('yolo swag swag yolo', reallyLong.slice(0, 19).toString());
 
 // Expensive reverse searches. Stress test lastIndexOf:

test/parallel/test-buffer-inspect.js

@@ -6,13 +6,13 @@ const buffer = require('buffer');
 
 buffer.INSPECT_MAX_BYTES = 2;
 
-var b = Buffer.allocUnsafe(4);
+let b = Buffer.allocUnsafe(4);
 b.fill('1234');
 
-var s = buffer.SlowBuffer(4);
+let s = buffer.SlowBuffer(4);
 s.fill('1234');
 
-var expected = '<Buffer 31 32 ... >';
+let expected = '<Buffer 31 32 ... >';
 
 assert.strictEqual(util.inspect(b), expected);
 assert.strictEqual(util.inspect(s), expected);

test/parallel/test-buffer-iterator.js

@@ -3,8 +3,8 @@ require('../common');
 const assert = require('assert');
 
 const buffer = Buffer.from([1, 2, 3, 4, 5]);
-var arr;
-var b;
+let arr;
+let b;
 
 // buffers should be iterable
 

test/parallel/test-buffer-swap.js

@@ -45,80 +45,80 @@ assert.deepStrictEqual(buf3_64, Buffer.from([0x01, 0x02, 0x0a, 0x09, 0x08, 0x07,
                                              0x0f, 0x10]));
 
 // Force use of native code (Buffer size above threshold limit for js impl)
-var buf4A = new Uint32Array(256).fill(0x04030201);
-var buf4 = Buffer.from(buf4A.buffer, buf4A.byteOffset);
-var buf5A = new Uint32Array(256).fill(0x03040102);
-var buf5 = Buffer.from(buf5A.buffer, buf5A.byteOffset);
+const buf4A = new Uint32Array(256).fill(0x04030201);
+const buf4 = Buffer.from(buf4A.buffer, buf4A.byteOffset);
+const buf5A = new Uint32Array(256).fill(0x03040102);
+const buf5 = Buffer.from(buf5A.buffer, buf5A.byteOffset);
 
 buf4.swap16();
 assert.deepStrictEqual(buf4, buf5);
 
-var buf6A = new Uint32Array(256).fill(0x04030201);
-var buf6 = Buffer.from(buf6A.buffer);
-var bu7A = new Uint32Array(256).fill(0x01020304);
-var buf7 = Buffer.from(bu7A.buffer, bu7A.byteOffset);
+const buf6A = new Uint32Array(256).fill(0x04030201);
+const buf6 = Buffer.from(buf6A.buffer);
+const bu7A = new Uint32Array(256).fill(0x01020304);
+const buf7 = Buffer.from(bu7A.buffer, bu7A.byteOffset);
 
 buf6.swap32();
 assert.deepStrictEqual(buf6, buf7);
 
-var buf8A = new Uint8Array(256 * 8);
-var buf9A = new Uint8Array(256 * 8);
+const buf8A = new Uint8Array(256 * 8);
+const buf9A = new Uint8Array(256 * 8);
 for (let i = 0; i < buf8A.length; i++) {
   buf8A[i] = i % 8;
   buf9A[buf9A.length - i - 1] = i % 8;
 }
-var buf8 = Buffer.from(buf8A.buffer, buf8A.byteOffset);
-var buf9 = Buffer.from(buf9A.buffer, buf9A.byteOffset);
+const buf8 = Buffer.from(buf8A.buffer, buf8A.byteOffset);
+const buf9 = Buffer.from(buf9A.buffer, buf9A.byteOffset);
 
 buf8.swap64();
 assert.deepStrictEqual(buf8, buf9);
 
 // Test native code with buffers that are not memory-aligned
-var buf10A = new Uint8Array(256 * 8);
-var buf11A = new Uint8Array(256 * 8 - 2);
+const buf10A = new Uint8Array(256 * 8);
+const buf11A = new Uint8Array(256 * 8 - 2);
 for (let i = 0; i < buf10A.length; i++) {
   buf10A[i] = i % 2;
 }
 for (let i = 1; i < buf11A.length; i++) {
   buf11A[buf11A.length - i] = (i + 1) % 2;
 }
-var buf10 = Buffer.from(buf10A.buffer, buf10A.byteOffset);
+const buf10 = Buffer.from(buf10A.buffer, buf10A.byteOffset);
 // 0|1 0|1 0|1...
-var buf11 = Buffer.from(buf11A.buffer, buf11A.byteOffset);
+const buf11 = Buffer.from(buf11A.buffer, buf11A.byteOffset);
 // 0|0 1|0 1|0...
 
 buf10.slice(1, buf10.length - 1).swap16();
 assert.deepStrictEqual(buf10.slice(0, buf11.length), buf11);
 
 
-var buf12A = new Uint8Array(256 * 8);
-var buf13A = new Uint8Array(256 * 8 - 4);
+const buf12A = new Uint8Array(256 * 8);
+const buf13A = new Uint8Array(256 * 8 - 4);
 for (let i = 0; i < buf12A.length; i++) {
   buf12A[i] = i % 4;
 }
 for (let i = 1; i < buf13A.length; i++) {
   buf13A[buf13A.length - i] = (i + 1) % 4;
 }
-var buf12 = Buffer.from(buf12A.buffer, buf12A.byteOffset);
+const buf12 = Buffer.from(buf12A.buffer, buf12A.byteOffset);
 // 0|1 2 3 0|1 2 3...
-var buf13 = Buffer.from(buf13A.buffer, buf13A.byteOffset);
+const buf13 = Buffer.from(buf13A.buffer, buf13A.byteOffset);
 // 0|0 3 2 1|0 3 2...
 
 buf12.slice(1, buf12.length - 3).swap32();
 assert.deepStrictEqual(buf12.slice(0, buf13.length), buf13);
 
 
-var buf14A = new Uint8Array(256 * 8);
-var buf15A = new Uint8Array(256 * 8 - 8);
+const buf14A = new Uint8Array(256 * 8);
+const buf15A = new Uint8Array(256 * 8 - 8);
 for (let i = 0; i < buf14A.length; i++) {
   buf14A[i] = i % 8;
 }
 for (let i = 1; i < buf15A.length; i++) {
   buf15A[buf15A.length - i] = (i + 1) % 8;
 }
-var buf14 = Buffer.from(buf14A.buffer, buf14A.byteOffset);
+const buf14 = Buffer.from(buf14A.buffer, buf14A.byteOffset);
 // 0|1 2 3 4 5 6 7 0|1 2 3 4...
-var buf15 = Buffer.from(buf15A.buffer, buf15A.byteOffset);
+const buf15 = Buffer.from(buf15A.buffer, buf15A.byteOffset);
 // 0|0 7 6 5 4 3 2 1|0 7 6 5...
 
 buf14.slice(1, buf14.length - 7).swap64();

test/parallel/test-child-process-constructor.js

@@ -3,11 +3,11 @@
 require('../common');
 const assert = require('assert');
 const child_process = require('child_process');
-var ChildProcess = child_process.ChildProcess;
+const ChildProcess = child_process.ChildProcess;
 assert.strictEqual(typeof ChildProcess, 'function');
 
 // test that we can call spawn
-var child = new ChildProcess();
+const child = new ChildProcess();
 child.spawn({
   file: process.execPath,
   args: ['--interactive'],

test/parallel/test-child-process-default-options.js

@@ -6,14 +6,14 @@ const spawn = require('child_process').spawn;
 
 process.env.HELLO = 'WORLD';
 
-var child;
+let child;
 if (common.isWindows) {
   child = spawn('cmd.exe', ['/c', 'set'], {});
 } else {
   child = spawn('/usr/bin/env', [], {});
 }
 
-var response = '';
+let response = '';
 
 child.stdout.setEncoding('utf8');
 

test/parallel/test-child-process-double-pipe.js

@@ -8,7 +8,7 @@ const spawn = require('child_process').spawn;
 // We're trying to reproduce:
 // $ echo "hello\nnode\nand\nworld" | grep o | sed s/o/a/
 
-var grep, sed, echo;
+let grep, sed, echo;
 
 if (common.isWindows) {
   grep = spawn('grep', ['--binary', 'o']),
@@ -82,7 +82,7 @@ grep.stdout.on('end', function(code) {
 });
 
 
-var result = '';
+let result = '';
 
 // print sed's output
 sed.stdout.on('data', function(data) {

test/parallel/test-child-process-env.js

@@ -4,14 +4,14 @@ const assert = require('assert');
 
 const spawn = require('child_process').spawn;
 
-var env = {
+const env = {
   'HELLO': 'WORLD'
 };
 Object.setPrototypeOf(env, {
   'FOO': 'BAR'
 });
 
-var child;
+let child;
 if (common.isWindows) {
   child = spawn('cmd.exe', ['/c', 'set'], {env: env});
 } else {
@@ -19,7 +19,7 @@ if (common.isWindows) {
 }
 
 
-var response = '';
+let response = '';
 
 child.stdout.setEncoding('utf8');
 

test/parallel/test-child-process-exec-cwd.js

@@ -3,7 +3,7 @@ const common = require('../common');
 const assert = require('assert');
 const exec = require('child_process').exec;
 
-var pwdcommand, dir;
+let pwdcommand, dir;
 
 if (common.isWindows) {
   pwdcommand = 'echo %cd%';

test/parallel/test-child-process-exec-stdout-stderr-data-string.js

@@ -4,8 +4,8 @@ const common = require('../common');
 const assert = require('assert');
 const exec = require('child_process').exec;
 
-var stdoutCalls = 0;
-var stderrCalls = 0;
+let stdoutCalls = 0;
+let stderrCalls = 0;
 
 const command = common.isWindows ? 'dir' : 'ls';
 exec(command).stdout.on('data', (data) => {

test/parallel/test-child-process-exit-code.js

@@ -4,17 +4,17 @@ const assert = require('assert');
 const spawn = require('child_process').spawn;
 const path = require('path');
 
-var exitScript = path.join(common.fixturesDir, 'exit.js');
-var exitChild = spawn(process.argv[0], [exitScript, 23]);
+const exitScript = path.join(common.fixturesDir, 'exit.js');
+const exitChild = spawn(process.argv[0], [exitScript, 23]);
 exitChild.on('exit', common.mustCall(function(code, signal) {
   assert.strictEqual(code, 23);
   assert.strictEqual(signal, null);
 }));
 
 
-var errorScript = path.join(common.fixturesDir,
-                            'child_process_should_emit_error.js');
-var errorChild = spawn(process.argv[0], [errorScript]);
+const errorScript = path.join(common.fixturesDir,
+                              'child_process_should_emit_error.js');
+const errorChild = spawn(process.argv[0], [errorScript]);
 errorChild.on('exit', common.mustCall(function(code, signal) {
   assert.ok(code !== 0);
   assert.strictEqual(signal, null);

test/parallel/test-child-process-fork-close.js

@@ -3,7 +3,7 @@ const common = require('../common');
 const assert = require('assert');
 const fork = require('child_process').fork;
 
-var cp = fork(common.fixturesDir + '/child-process-message-and-exit.js');
+const cp = fork(common.fixturesDir + '/child-process-message-and-exit.js');
 
 let gotMessage = false;
 let gotExit = false;

test/parallel/test-child-process-fork-dgram.js

@@ -37,8 +37,8 @@ if (process.argv[2] === 'child') {
 
   const msg = Buffer.from('Some bytes');
 
-  var childGotMessage = false;
-  var parentGotMessage = false;
+  let childGotMessage = false;
+  let parentGotMessage = false;
 
   parentServer.once('message', function(msg, rinfo) {
     parentGotMessage = true;

test/parallel/test-child-process-fork-exec-argv.js

@@ -2,8 +2,8 @@
 require('../common');
 const assert = require('assert');
 const child_process = require('child_process');
-var spawn = child_process.spawn;
-var fork = child_process.fork;
+const spawn = child_process.spawn;
+const fork = child_process.fork;
 
 if (process.argv[2] === 'fork') {
   process.stdout.write(JSON.stringify(process.execArgv), function() {
@@ -12,11 +12,11 @@ if (process.argv[2] === 'fork') {
 } else if (process.argv[2] === 'child') {
   fork(__filename, ['fork']);
 } else {
-  var execArgv = ['--stack-size=256'];
-  var args = [__filename, 'child', 'arg0'];
+  const execArgv = ['--stack-size=256'];
+  const args = [__filename, 'child', 'arg0'];
 
-  var child = spawn(process.execPath, execArgv.concat(args));
-  var out = '';
+  const child = spawn(process.execPath, execArgv.concat(args));
+  let out = '';
 
   child.stdout.on('data', function(chunk) {
     out += chunk;

test/parallel/test-child-process-fork-exec-path.js

@@ -3,9 +3,9 @@ const common = require('../common');
 const assert = require('assert');
 const fs = require('fs');
 const path = require('path');
-var msg = {test: 'this'};
-var nodePath = process.execPath;
-var copyPath = path.join(common.tmpDir, 'node-copy.exe');
+const msg = {test: 'this'};
+const nodePath = process.execPath;
+const copyPath = path.join(common.tmpDir, 'node-copy.exe');
 
 if (process.env.FORK) {
   assert(process.send);
@@ -23,7 +23,7 @@ if (process.env.FORK) {
   fs.chmodSync(copyPath, '0755');
 
   // slow but simple
-  var envCopy = JSON.parse(JSON.stringify(process.env));
+  const envCopy = JSON.parse(JSON.stringify(process.env));
   envCopy.FORK = 'true';
   const child = require('child_process').fork(__filename, {
     execPath: copyPath,

test/parallel/test-child-process-fork-net.js

@@ -19,7 +19,7 @@ ProgressTracker.prototype.check = function() {
 
 if (process.argv[2] === 'child') {
 
-  var serverScope;
+  let serverScope;
 
   process.on('message', function onServer(msg, server) {
     if (msg.what !== 'server') return;
@@ -58,17 +58,17 @@ if (process.argv[2] === 'child') {
   process.send({what: 'ready'});
 } else {
 
-  var child = fork(process.argv[1], ['child']);
+  const child = fork(process.argv[1], ['child']);
 
   child.on('exit', function() {
     console.log('CHILD: died');
   });
 
   // send net.Server to child and test by connecting
-  var testServer = function(callback) {
+  const testServer = function(callback) {
 
     // destroy server execute callback when done
-    var progress = new ProgressTracker(2, function() {
+    const progress = new ProgressTracker(2, function() {
       server.on('close', function() {
         console.log('PARENT: server closed');
         child.send({what: 'close'});
@@ -77,11 +77,11 @@ if (process.argv[2] === 'child') {
     });
 
     // we expect 4 connections and close events
-    var connections = new ProgressTracker(4, progress.done.bind(progress));
-    var closed = new ProgressTracker(4, progress.done.bind(progress));
+    const connections = new ProgressTracker(4, progress.done.bind(progress));
+    const closed = new ProgressTracker(4, progress.done.bind(progress));
 
     // create server and send it to child
-    var server = net.createServer();
+    const server = net.createServer();
     server.on('connection', function(socket) {
       console.log('PARENT: got connection');
       socket.destroy();
@@ -94,12 +94,12 @@ if (process.argv[2] === 'child') {
     server.listen(0);
 
     // handle client messages
-    var messageHandlers = function(msg) {
+    const messageHandlers = function(msg) {
 
       if (msg.what === 'listening') {
         // make connections
-        var socket;
-        for (var i = 0; i < 4; i++) {
+        let socket;
+        for (let i = 0; i < 4; i++) {
           socket = net.connect(server.address().port, function() {
             console.log('CLIENT: connected');
           });
@@ -122,11 +122,11 @@ if (process.argv[2] === 'child') {
   };
 
   // send net.Socket to child
-  var testSocket = function(callback) {
+  const testSocket = function(callback) {
 
     // create a new server and connect to it,
     // but the socket will be handled by the child
-    var server = net.createServer();
+    const server = net.createServer();
     server.on('connection', function(socket) {
       socket.on('close', function() {
         console.log('CLIENT: socket closed');
@@ -145,8 +145,8 @@ if (process.argv[2] === 'child') {
     // will have to do.
     server.listen(0, function() {
       console.error('testSocket, listening');
-      var connect = net.connect(server.address().port);
-      var store = '';
+      const connect = net.connect(server.address().port);
+      let store = '';
       connect.on('data', function(chunk) {
         store += chunk;
         console.log('CLIENT: got data');
@@ -160,8 +160,8 @@ if (process.argv[2] === 'child') {
   };
 
   // create server and send it to child
-  var serverSuccess = false;
-  var socketSuccess = false;
+  let serverSuccess = false;
+  let socketSuccess = false;
   child.on('message', function onReady(msg) {
     if (msg.what !== 'ready') return;
     child.removeListener('message', onReady);

test/parallel/test-child-process-fork-net2.js

@@ -3,11 +3,11 @@ const common = require('../common');
 const assert = require('assert');
 const fork = require('child_process').fork;
 const net = require('net');
-var count = 12;
+const count = 12;
 
 if (process.argv[2] === 'child') {
-  var needEnd = [];
-  var id = process.argv[3];
+  const needEnd = [];
+  const id = process.argv[3];
 
   process.on('message', function(m, socket) {
     if (!socket) return;
@@ -60,11 +60,11 @@ if (process.argv[2] === 'child') {
 
 } else {
 
-  var child1 = fork(process.argv[1], ['child', '1']);
-  var child2 = fork(process.argv[1], ['child', '2']);
-  var child3 = fork(process.argv[1], ['child', '3']);
+  const child1 = fork(process.argv[1], ['child', '1']);
+  const child2 = fork(process.argv[1], ['child', '2']);
+  const child3 = fork(process.argv[1], ['child', '3']);
 
-  var server = net.createServer();
+  const server = net.createServer();
 
   let connected = 0;
   let closed = 0;
@@ -94,10 +94,10 @@ if (process.argv[2] === 'child') {
     }
   });
 
-  var disconnected = 0;
+  let disconnected = 0;
   server.on('listening', function() {
 
-    var j = count, client;
+    let j = count, client;
     while (j--) {
       client = net.connect(this.address().port, '127.0.0.1');
       client.on('error', function() {
@@ -112,7 +112,7 @@ if (process.argv[2] === 'child') {
     }
   });
 
-  var closeEmitted = false;
+  let closeEmitted = false;
   server.on('close', common.mustCall(function() {
     closeEmitted = true;
 
@@ -123,7 +123,7 @@ if (process.argv[2] === 'child') {
 
   server.listen(0, '127.0.0.1');
 
-  var closeServer = function() {
+  const closeServer = function() {
     server.close();
 
     setTimeout(function() {

test/parallel/test-child-process-fork-ref.js

@@ -16,9 +16,10 @@ if (process.argv[2] === 'child') {
   });
 
 } else {
-  var child = fork(__filename, ['child'], {silent: true});
+  const child = fork(__filename, ['child'], {silent: true});
 
-  var ipc = [], stdout = '';
+  const ipc = [];
+  let stdout = '';
 
   child.on('message', function(msg) {
     ipc.push(msg);

test/parallel/test-child-process-fork-ref2.js

@@ -12,7 +12,7 @@ if (process.argv[2] === 'child') {
   }, 400);
 
 } else {
-  var child = fork(__filename, ['child']);
+  const child = fork(__filename, ['child']);
 
   child.on('disconnect', function() {
     console.log('parent -> disconnect');

test/parallel/test-child-process-fork-regr-gh-2847.js

@@ -14,7 +14,7 @@ if (!cluster.isMaster) {
   return;
 }
 
-var server = net.createServer(function(s) {
+const server = net.createServer(function(s) {
   if (common.isWindows) {
     s.on('error', function(err) {
       // Prevent possible ECONNRESET errors from popping up
@@ -26,10 +26,10 @@ var server = net.createServer(function(s) {
     s.destroy();
   }, 100);
 }).listen(0, function() {
-  var worker = cluster.fork();
+  const worker = cluster.fork();
 
   function send(callback) {
-    var s = net.connect(server.address().port, function() {
+    const s = net.connect(server.address().port, function() {
       worker.send({}, s, callback);
     });
 

test/parallel/test-child-process-fork.js

@@ -2,9 +2,9 @@
 const common = require('../common');
 const assert = require('assert');
 const fork = require('child_process').fork;
-var args = ['foo', 'bar'];
+const args = ['foo', 'bar'];
 
-var n = fork(common.fixturesDir + '/child-process-spawn-node.js', args);
+const n = fork(common.fixturesDir + '/child-process-spawn-node.js', args);
 
 assert.strictEqual(n.channel, n._channel);
 assert.deepStrictEqual(args, ['foo', 'bar']);

test/parallel/test-child-process-internal.js

@@ -3,9 +3,9 @@ const common = require('../common');
 const assert = require('assert');
 
 //messages
-var PREFIX = 'NODE_';
-var normal = {cmd: 'foo' + PREFIX};
-var internal = {cmd: PREFIX + 'bar'};
+const PREFIX = 'NODE_';
+const normal = {cmd: 'foo' + PREFIX};
+const internal = {cmd: PREFIX + 'bar'};
 
 if (process.argv[2] === 'child') {
   //send non-internal message containing PREFIX at a non prefix position
@@ -19,7 +19,7 @@ if (process.argv[2] === 'child') {
 } else {
 
   const fork = require('child_process').fork;
-  var child = fork(process.argv[1], ['child']);
+  const child = fork(process.argv[1], ['child']);
 
   child.once('message', common.mustCall(function(data) {
     assert.deepStrictEqual(data, normal);

test/parallel/test-child-process-send-returns-boolean.js

@@ -15,7 +15,7 @@ assert.strictEqual(rv, true);
 
 const spawnOptions = { stdio: ['pipe', 'pipe', 'pipe', 'ipc'] };
 const s = spawn(process.execPath, [emptyFile], spawnOptions);
-var handle = null;
+let handle = null;
 s.on('exit', function() {
   handle.close();
 });

test/parallel/test-child-process-set-blocking.js

@@ -3,9 +3,9 @@ const common = require('../common');
 const assert = require('assert');
 const ch = require('child_process');
 
-var SIZE = 100000;
+const SIZE = 100000;
 
-var cp = ch.spawn('python', ['-c', 'print ' + SIZE + ' * "C"'], {
+const cp = ch.spawn('python', ['-c', 'print ' + SIZE + ' * "C"'], {
   stdio: 'inherit'
 });
 

test/parallel/test-child-process-silent.js

@@ -32,15 +32,15 @@ if (process.argv[2] === 'pipe') {
   // testcase | start parent && child IPC test
 
   // testing: is stderr and stdout piped to parent
-  var args = [process.argv[1], 'parent'];
-  var parent = childProcess.spawn(process.execPath, args);
+  const args = [process.argv[1], 'parent'];
+  const parent = childProcess.spawn(process.execPath, args);
 
   //got any stderr or std data
-  var stdoutData = false;
+  let stdoutData = false;
   parent.stdout.on('data', function() {
     stdoutData = true;
   });
-  var stderrData = false;
+  let stderrData = false;
   parent.stdout.on('data', function() {
     stderrData = true;
   });
@@ -52,8 +52,8 @@ if (process.argv[2] === 'pipe') {
   child.stderr.pipe(process.stderr, {end: false});
   child.stdout.pipe(process.stdout, {end: false});
 
-  var childSending = false;
-  var childReciveing = false;
+  let childSending = false;
+  let childReciveing = false;
   child.on('message', function(message) {
     if (childSending === false) {
       childSending = (message === 'message from child');

test/parallel/test-child-process-spawn-typeerror.js

@@ -14,7 +14,7 @@ const invalidFileMsg =
 const empty = common.fixturesDir + '/empty.js';
 
 assert.throws(function() {
-  var child = spawn(invalidcmd, 'this is not an array');
+  const child = spawn(invalidcmd, 'this is not an array');
   child.on('error', common.fail);
 }, TypeError);
 

test/parallel/test-child-process-spawnsync-env.js

@@ -6,8 +6,8 @@ const cp = require('child_process');
 if (process.argv[2] === 'child') {
   console.log(process.env.foo);
 } else {
-  var expected = 'bar';
-  var child = cp.spawnSync(process.execPath, [__filename, 'child'], {
+  const expected = 'bar';
+  const child = cp.spawnSync(process.execPath, [__filename, 'child'], {
     env: Object.assign(process.env, { foo: expected })
   });
 

test/parallel/test-child-process-spawnsync-input.js

@@ -17,7 +17,7 @@ const args = [
   `console.log("${msgOut}"); console.error("${msgErr}");`
 ];
 
-var ret;
+let ret;
 
 
 function checkSpawnSyncRet(ret) {
@@ -51,7 +51,7 @@ if (process.argv.indexOf('spawnchild') !== -1) {
 verifyBufOutput(spawnSync(process.execPath, [__filename, 'spawnchild', 1]));
 verifyBufOutput(spawnSync(process.execPath, [__filename, 'spawnchild', 2]));
 
-var options = {
+let options = {
   input: 1234
 };
 

test/parallel/test-child-process-spawnsync-timeout.js

@@ -4,8 +4,8 @@ const assert = require('assert');
 
 const spawnSync = require('child_process').spawnSync;
 
-var TIMER = 200;
-var SLEEP = 5000;
+const TIMER = 200;
+const SLEEP = 5000;
 
 switch (process.argv[2]) {
   case 'child':
@@ -15,12 +15,12 @@ switch (process.argv[2]) {
     }, SLEEP);
     break;
   default:
-    var start = Date.now();
-    var ret = spawnSync(process.execPath, [__filename, 'child'],
+    const start = Date.now();
+    const ret = spawnSync(process.execPath, [__filename, 'child'],
                         {timeout: TIMER});
     assert.strictEqual(ret.error.errno, 'ETIMEDOUT');
     console.log(ret);
-    var end = Date.now() - start;
+    const end = Date.now() - start;
     assert(end < SLEEP);
     assert(ret.status > 128 || ret.signal);
     break;

test/parallel/test-child-process-stdin-ipc.js

@@ -10,7 +10,7 @@ if (process.argv[2] === 'child') {
   return;
 }
 
-var proc = spawn(process.execPath, [__filename, 'child'], {
+const proc = spawn(process.execPath, [__filename, 'child'], {
   stdio: ['ipc', 'inherit', 'inherit']
 });
 

test/parallel/test-child-process-stdio-big-write-end.js

@@ -28,8 +28,9 @@ function parent() {
   });
 
   // Write until the buffer fills up.
+  let buf;
   do {
-    var buf = Buffer.alloc(BUFSIZE, '.');
+    buf = Buffer.alloc(BUFSIZE, '.');
     sent += BUFSIZE;
   } while (child.stdin.write(buf));
 

test/parallel/test-child-process-stdio-inherit.js

@@ -9,10 +9,10 @@ else
   grandparent();
 
 function grandparent() {
-  var child = spawn(process.execPath, [__filename, 'parent']);
+  const child = spawn(process.execPath, [__filename, 'parent']);
   child.stderr.pipe(process.stderr);
-  var output = '';
-  var input = 'asdfasdf';
+  let output = '';
+  const input = 'asdfasdf';
 
   child.stdout.on('data', function(chunk) {
     output += chunk;

test/parallel/test-cli-eval.js

@@ -14,7 +14,7 @@ const nodejs = '"' + process.execPath + '"';
 
 // replace \ by / because windows uses backslashes in paths, but they're still
 // interpreted as the escape character when put between quotes.
-var filename = __filename.replace(/\\/g, '/');
+const filename = __filename.replace(/\\/g, '/');
 
 // assert that nothing is written to stdout
 child.exec(nodejs + ' --eval 42',
@@ -32,7 +32,7 @@ child.exec(nodejs + ' --eval "console.error(42)"',
 
 // assert that the expected output is written to stdout
 ['--print', '-p -e', '-pe', '-p'].forEach(function(s) {
-  var cmd = nodejs + ' ' + s + ' ';
+  const cmd = nodejs + ' ' + s + ' ';
 
   child.exec(cmd + '42',
              function(err, stdout, stderr) {

test/parallel/test-cli-syntax.js

@@ -5,10 +5,10 @@ const assert = require('assert');
 const spawnSync = require('child_process').spawnSync;
 const path = require('path');
 
-var node = process.execPath;
+const node = process.execPath;
 
 // test both sets of arguments that check syntax
-var syntaxArgs = [
+const syntaxArgs = [
   ['-c'],
   ['--check']
 ];
@@ -25,8 +25,8 @@ var syntaxArgs = [
 
   // loop each possible option, `-c` or `--check`
   syntaxArgs.forEach(function(args) {
-    var _args = args.concat(file);
-    var c = spawnSync(node, _args, {encoding: 'utf8'});
+    const _args = args.concat(file);
+    const c = spawnSync(node, _args, {encoding: 'utf8'});
 
     // no output should be produced
     assert.strictEqual(c.stdout, '', 'stdout produced');
@@ -46,14 +46,14 @@ var syntaxArgs = [
 
   // loop each possible option, `-c` or `--check`
   syntaxArgs.forEach(function(args) {
-    var _args = args.concat(file);
-    var c = spawnSync(node, _args, {encoding: 'utf8'});
+    const _args = args.concat(file);
+    const c = spawnSync(node, _args, {encoding: 'utf8'});
 
     // no stdout should be produced
     assert.strictEqual(c.stdout, '', 'stdout produced');
 
     // stderr should have a syntax error message
-    var match = c.stderr.match(/^SyntaxError: Unexpected identifier$/m);
+    const match = c.stderr.match(/^SyntaxError: Unexpected identifier$/m);
     assert(match, 'stderr incorrect');
 
     assert.strictEqual(c.status, 1, 'code == ' + c.status);
@@ -69,14 +69,14 @@ var syntaxArgs = [
 
   // loop each possible option, `-c` or `--check`
   syntaxArgs.forEach(function(args) {
-    var _args = args.concat(file);
-    var c = spawnSync(node, _args, {encoding: 'utf8'});
+    const _args = args.concat(file);
+    const c = spawnSync(node, _args, {encoding: 'utf8'});
 
     // no stdout should be produced
     assert.strictEqual(c.stdout, '', 'stdout produced');
 
     // stderr should have a module not found error message
-    var match = c.stderr.match(/^Error: Cannot find module/m);
+    const match = c.stderr.match(/^Error: Cannot find module/m);
     assert(match, 'stderr incorrect');
 
     assert.strictEqual(c.status, 1, 'code == ' + c.status);

test/parallel/test-cluster-basic.js

@@ -56,7 +56,6 @@ if (cluster.isWorker) {
     }
   };
 
-  var worker;
   const stateNames = Object.keys(checks.worker.states);
 
   //Check events, states, and emit arguments
@@ -72,7 +71,7 @@ if (cluster.isWorker) {
       checks.cluster.equal[name] = worker === arguments[0];
 
       //Check state
-      var state = stateNames[index];
+      const state = stateNames[index];
       checks.worker.states[state] = (state === worker.state);
     }));
   });
@@ -86,7 +85,7 @@ if (cluster.isWorker) {
   cluster.on('exit', common.mustCall(() => {}));
 
   //Create worker
-  worker = cluster.fork();
+  const worker = cluster.fork();
   assert.strictEqual(worker.id, 1);
   assert(worker instanceof cluster.Worker,
          'the worker is not a instance of the Worker constructor');

test/parallel/test-cluster-bind-privileged-port.js

@@ -19,7 +19,7 @@ if (cluster.isMaster) {
     assert.strictEqual(exitCode, 0);
   }));
 } else {
-  var s = net.createServer(common.fail);
+  const s = net.createServer(common.fail);
   s.listen(42, common.fail.bind(null, 'listen should have failed'));
   s.on('error', common.mustCall((err) => {
     assert.strictEqual(err.code, 'EACCES');

test/parallel/test-cluster-dgram-1.js

@@ -21,10 +21,10 @@ else
 
 
 function master() {
-  var listening = 0;
+  let listening = 0;
 
   // Fork 4 workers.
-  for (var i = 0; i < NUM_WORKERS; i++)
+  for (let i = 0; i < NUM_WORKERS; i++)
     cluster.fork();
 
   // Wait until all workers are listening.
@@ -35,7 +35,7 @@ function master() {
     // Start sending messages.
     const buf = Buffer.from('hello world');
     const socket = dgram.createSocket('udp4');
-    var sent = 0;
+    let sent = 0;
     doSend();
 
     function doSend() {
@@ -60,7 +60,7 @@ function master() {
   }
 
   function setupWorker(worker) {
-    var received = 0;
+    let received = 0;
 
     worker.on('message', common.mustCall((msg) => {
       received = msg.received;
@@ -75,10 +75,10 @@ function master() {
 
 
 function worker() {
-  var received = 0;
+  let received = 0;
 
   // Create udp socket and start listening.
-  var socket = dgram.createSocket('udp4');
+  const socket = dgram.createSocket('udp4');
 
   socket.on('message', common.mustCall((data, info) => {
     received++;

test/parallel/test-cluster-dgram-2.js

@@ -20,10 +20,10 @@ else
 
 
 function master() {
-  var received = 0;
+  let received = 0;
 
   // Start listening on a socket.
-  var socket = dgram.createSocket('udp4');
+  const socket = dgram.createSocket('udp4');
   socket.bind(common.PORT);
 
   // Disconnect workers when the expected number of messages have been
@@ -42,7 +42,7 @@ function master() {
   }, NUM_WORKERS * PACKETS_PER_WORKER));
 
   // Fork workers.
-  for (var i = 0; i < NUM_WORKERS; i++)
+  for (let i = 0; i < NUM_WORKERS; i++)
     cluster.fork();
 }
 

test/parallel/test-cluster-dgram-reuse.js

@@ -25,16 +25,16 @@ function next() {
 
   // Work around health check issue
   process.nextTick(() => {
-    for (var i = 0; i < sockets.length; i++)
+    for (let i = 0; i < sockets.length; i++)
       sockets[i].close(close);
   });
 }
 
-var waiting = 2;
+let waiting = 2;
 function close() {
   if (--waiting === 0)
     cluster.worker.disconnect();
 }
 
-for (var i = 0; i < 2; i++)
+for (let i = 0; i < 2; i++)
   dgram.createSocket({ type: 'udp4', reuseAddr: true }).bind(common.PORT, next);

test/parallel/test-cluster-disconnect-race.js

@@ -16,9 +16,9 @@ if (common.isWindows) {
 cluster.schedulingPolicy = cluster.SCHED_NONE;
 
 if (cluster.isMaster) {
-  var worker1, worker2;
+  let worker2;
 
-  worker1 = cluster.fork();
+  const worker1 = cluster.fork();
   worker1.on('message', common.mustCall(function() {
     worker2 = cluster.fork();
     worker1.disconnect();
@@ -32,7 +32,7 @@ if (cluster.isMaster) {
   return;
 }
 
-var server = net.createServer();
+const server = net.createServer();
 
 server.listen(common.PORT, function() {
   process.send('listening');

test/parallel/test-cluster-disconnect-suicide-race.js

@@ -14,7 +14,7 @@ if (cluster.isMaster) {
   return cluster.fork();
 }
 
-var eventFired = false;
+let eventFired = false;
 
 cluster.worker.disconnect();
 

test/parallel/test-cluster-disconnect-with-no-workers.js

@@ -3,7 +3,7 @@ require('../common');
 const assert = require('assert');
 const cluster = require('cluster');
 
-var disconnected;
+let disconnected;
 
 process.on('exit', function() {
   assert(disconnected);

test/parallel/test-cluster-disconnect.js

@@ -14,13 +14,13 @@ if (cluster.isWorker) {
   }).listen(common.PORT + 1, '127.0.0.1');
 
 } else if (cluster.isMaster) {
-  var servers = 2;
+  const servers = 2;
 
   // test a single TCP server
   const testConnection = function(port, cb) {
-    var socket = net.connect(port, '127.0.0.1', () => {
+    const socket = net.connect(port, '127.0.0.1', () => {
       // buffer result
-      var result = '';
+      let result = '';
       socket.on('data', common.mustCall((chunk) => { result += chunk; }));
 
       // check result
@@ -32,9 +32,9 @@ if (cluster.isWorker) {
 
   // test both servers created in the cluster
   const testCluster = function(cb) {
-    var done = 0;
+    let done = 0;
 
-    for (var i = 0, l = servers; i < l; i++) {
+    for (let i = 0, l = servers; i < l; i++) {
       testConnection(common.PORT + i, (success) => {
         assert.ok(success);
         done += 1;
@@ -47,10 +47,10 @@ if (cluster.isWorker) {
 
   // start two workers and execute callback when both is listening
   const startCluster = function(cb) {
-    var workers = 8;
-    var online = 0;
+    const workers = 8;
+    let online = 0;
 
-    for (var i = 0, l = workers; i < l; i++) {
+    for (let i = 0, l = workers; i < l; i++) {
       cluster.fork().on('listening', common.mustCall(() => {
         online += 1;
         if (online === workers * servers) {

test/parallel/test-cluster-eaccess.js

@@ -37,7 +37,7 @@ if (cluster.isMaster) {
 
 } else {
   common.refreshTmpDir();
-  var cp = fork(common.fixturesDir + '/listen-on-socket-and-exit.js',
+  const cp = fork(common.fixturesDir + '/listen-on-socket-and-exit.js',
                 { stdio: 'inherit' });
 
   // message from the child indicates it's ready and listening

test/parallel/test-cluster-eaddrinuse.js

@@ -8,12 +8,12 @@ const assert = require('assert');
 const fork = require('child_process').fork;
 const net = require('net');
 
-var id = '' + process.argv[2];
+const id = '' + process.argv[2];
 
 if (id === 'undefined') {
   const server = net.createServer(common.fail);
   server.listen(common.PORT, function() {
-    var worker = fork(__filename, ['worker']);
+    const worker = fork(__filename, ['worker']);
     worker.on('message', function(msg) {
       if (msg !== 'stop-listening') return;
       server.close(function() {

test/parallel/test-cluster-fork-env.js

@@ -12,7 +12,7 @@ if (cluster.isWorker) {
   assert.strictEqual(result, true);
 } else if (cluster.isMaster) {
 
-  var checks = {
+  const checks = {
     using: false,
     overwrite: false
   };
@@ -22,7 +22,7 @@ if (cluster.isWorker) {
   process.env['cluster_test_overwrite'] = 'old';
 
   // Fork worker
-  var worker = cluster.fork({
+  const worker = cluster.fork({
     'cluster_test_prop': 'custom',
     'cluster_test_overwrite': 'new'
   });

test/parallel/test-cluster-master-error.js

@@ -15,7 +15,7 @@ if (cluster.isWorker) {
 } else if (process.argv[2] === 'cluster') {
 
   // Send PID to testcase process
-  var forkNum = 0;
+  let forkNum = 0;
   cluster.on('fork', common.mustCall(function forkEvent(worker) {
 
     // Send PID
@@ -31,7 +31,7 @@ if (cluster.isWorker) {
   }));
 
   // Throw accidental error when all workers are listening
-  var listeningNum = 0;
+  let listeningNum = 0;
   cluster.on('listening', common.mustCall(function listeningEvent() {
 
     // When all workers are listening
@@ -56,8 +56,8 @@ if (cluster.isWorker) {
 
   const fork = require('child_process').fork;
 
-  var masterExited = false;
-  var workersExited = false;
+  let masterExited = false;
+  let workersExited = false;
 
   // List all workers
   const workers = [];
@@ -82,7 +82,7 @@ if (cluster.isWorker) {
 
     const pollWorkers = function() {
       // When master is dead all workers should be dead too
-      var alive = false;
+      let alive = false;
       workers.forEach((pid) => alive = common.isAlive(pid));
       if (alive) {
         setTimeout(pollWorkers, 50);

test/parallel/test-cluster-master-kill.js

@@ -34,13 +34,13 @@ if (cluster.isWorker) {
   const master = fork(process.argv[1], ['cluster']);
 
   // get pid info
-  var pid = null;
+  let pid = null;
   master.once('message', (data) => {
     pid = data.pid;
   });
 
   // When master is dead
-  var alive = true;
+  let alive = true;
   master.on('exit', common.mustCall((code) => {
 
     // make sure that the master died on purpose

test/parallel/test-cluster-message.js

@@ -13,8 +13,8 @@ function forEach(obj, fn) {
 if (cluster.isWorker) {
   // Create a tcp server. This will be used as cluster-shared-server and as an
   // alternative IPC channel.
-  var server = net.Server();
-  var socket, message;
+  const server = net.Server();
+  let socket, message;
 
   function maybeReply() {
     if (!socket || !message) return;
@@ -42,7 +42,7 @@ if (cluster.isWorker) {
   server.listen(common.PORT, '127.0.0.1');
 } else if (cluster.isMaster) {
 
-  var checks = {
+  const checks = {
     global: {
       'receive': false,
       'correct': false
@@ -58,13 +58,13 @@ if (cluster.isWorker) {
   };
 
 
-  var client;
-  var check = function(type, result) {
+  let client;
+  const check = function(type, result) {
     checks[type].receive = true;
     checks[type].correct = result;
     console.error('check', checks);
 
-    var missing = false;
+    let missing = false;
     forEach(checks, function(type) {
       if (type.receive === false) missing = true;
     });
@@ -76,7 +76,7 @@ if (cluster.isWorker) {
   };
 
   // Spawn worker
-  var worker = cluster.fork();
+  const worker = cluster.fork();
 
   // When a IPC message is received from the worker
   worker.on('message', function(message) {

test/parallel/test-cluster-rr-domain-listen.js

@@ -7,14 +7,13 @@ const domain = require('domain');
 // cluster.schedulingPolicy = cluster.SCHED_RR;
 
 if (cluster.isWorker) {
-  var d = domain.create();
+  const d = domain.create();
   d.run(function() { });
 
   const http = require('http');
   http.Server(function() { }).listen(common.PORT, '127.0.0.1');
 
 } else if (cluster.isMaster) {
-  var worker;
 
   //Kill worker when listening
   cluster.on('listening', function() {
@@ -27,5 +26,5 @@ if (cluster.isWorker) {
   });
 
   //Create worker
-  worker = cluster.fork();
+  const worker = cluster.fork();
 }

test/parallel/test-cluster-send-deadlock.js

@@ -8,14 +8,14 @@ const cluster = require('cluster');
 const net = require('net');
 
 if (cluster.isMaster) {
-  var worker = cluster.fork();
+  const worker = cluster.fork();
   worker.on('exit', function(code, signal) {
     assert.strictEqual(code, 0, 'Worker exited with an error code');
     assert(!signal, 'Worker exited by a signal');
     server.close();
   });
 
-  var server = net.createServer(function(socket) {
+  const server = net.createServer(function(socket) {
     worker.send('handle', socket);
   });
 
@@ -25,9 +25,9 @@ if (cluster.isMaster) {
 } else {
   process.on('message', function(msg, handle) {
     if (msg === 'listen') {
-      var client1 = net.connect({ host: 'localhost', port: common.PORT });
-      var client2 = net.connect({ host: 'localhost', port: common.PORT });
-      var waiting = 2;
+      const client1 = net.connect({ host: 'localhost', port: common.PORT });
+      const client2 = net.connect({ host: 'localhost', port: common.PORT });
+      let waiting = 2;
       client1.on('close', onclose);
       client2.on('close', onclose);
       function onclose() {

test/parallel/test-cluster-setup-master-argv.js

@@ -6,8 +6,8 @@ const cluster = require('cluster');
 setTimeout(common.fail.bind(assert, 'setup not emitted'), 1000).unref();
 
 cluster.on('setup', common.mustCall(function() {
-  var clusterArgs = cluster.settings.args;
-  var realArgs = process.argv;
+  const clusterArgs = cluster.settings.args;
+  const realArgs = process.argv;
   assert.strictEqual(clusterArgs[clusterArgs.length - 1],
                      realArgs[realArgs.length - 1]);
 }));

test/parallel/test-cluster-setup-master-multiple.js

@@ -13,7 +13,7 @@ function cheapClone(obj) {
   return JSON.parse(JSON.stringify(obj));
 }
 
-var configs = [];
+const configs = [];
 
 // Capture changes
 cluster.on('setup', function() {
@@ -21,7 +21,7 @@ cluster.on('setup', function() {
   configs.push(cheapClone(cluster.settings));
 });
 
-var execs = [
+const execs = [
   'node-next',
   'node-next-2',
   'node-next-3',

test/parallel/test-cluster-setup-master.js

@@ -10,14 +10,14 @@ if (cluster.isWorker) {
 
 } else if (cluster.isMaster) {
 
-  var checks = {
+  const checks = {
     args: false,
     setupEvent: false,
     settingsObject: false
   };
 
-  var totalWorkers = 2;
-  var onlineWorkers = 0;
+  const totalWorkers = 2;
+  let onlineWorkers = 0;
 
   // Setup master
   cluster.setupMaster({
@@ -28,7 +28,7 @@ if (cluster.isWorker) {
   cluster.once('setup', function() {
     checks.setupEvent = true;
 
-    var settings = cluster.settings;
+    const settings = cluster.settings;
     if (settings &&
         settings.args && settings.args[0] === 'custom argument' &&
         settings.silent === true &&
@@ -37,7 +37,7 @@ if (cluster.isWorker) {
     }
   });
 
-  var correctIn = 0;
+  let correctIn = 0;
 
   cluster.on('online', function lisenter(worker) {
 
@@ -66,7 +66,7 @@ if (cluster.isWorker) {
     assert.ok(checks.workers, 'Not all workers went online');
     assert.ok(checks.args, 'The arguments was noy send to the worker');
     assert.ok(checks.setupEvent, 'The setup event was never emitted');
-    var m = 'The settingsObject do not have correct properties';
+    const m = 'The settingsObject do not have correct properties';
     assert.ok(checks.settingsObject, m);
   });