@ -50,9 +50,9 @@ Almost all Node.js programs, no matter how simple, use Streams in some
way. Here is an example of using Streams in an Node.js program:way. Here is an example of using Streams in an Node.js program:
```javascript```javascript
var http = require('http');const http = require('http');
var server = http.createServer(function (req, res) {var server = http.createServer( (req, res) => {
// req is an http.IncomingMessage, which is a Readable Stream // req is an http.IncomingMessage, which is a Readable Stream
// res is an http.ServerResponse, which is a Writable Stream // res is an http.ServerResponse, which is a Writable Stream
@ -62,18 +62,18 @@ var server = http.createServer(function (req, res) {
req.setEncoding('utf8'); req.setEncoding('utf8');
// Readable streams emit 'data' events once a listener is added // Readable streams emit 'data' events once a listener is added
req.on('data', function (chunk) { req.on('data', (chunk) => {
body += chunk; body += chunk;
}); });
// the end event tells you that you have entire body // the end event tells you that you have entire body
req.on('end', function () { req.on('end', () => {
try { try {
var data = JSON.parse(body); var data = JSON.parse(body);
} catch (er) { } catch (er) {
// uh oh! bad json! // uh oh! bad json!
res.statusCode = 400; res.statusCode = 400;
return res.end('error: ' + er.message ); return res.end(`error: ${er.message}` );
} }
// write back something interesting to the user: // write back something interesting to the user:
@ -176,7 +176,7 @@ possible, this is the best way to do so.
```javascript```javascript
var readable = getReadableStreamSomehow();var readable = getReadableStreamSomehow();
readable.on('data', function (chunk) {readable.on('data', (chunk) => {
console.log('got %d bytes of data', chunk.length); console.log('got %d bytes of data', chunk.length);
});});
``````
@ -191,10 +191,10 @@ or by calling `read()` repeatedly until you get to the end.
```javascript```javascript
var readable = getReadableStreamSomehow();var readable = getReadableStreamSomehow();
readable.on('data', function (chunk) {readable.on('data', (chunk) => {
console.log('got %d bytes of data', chunk.length); console.log('got %d bytes of data', chunk.length);
});});
readable.on('end', function () {readable.on('end', () => {
console.log('there will be no more data.'); console.log('there will be no more data.');
});});
``````
@ -216,7 +216,7 @@ hadn't already.
```javascript```javascript
var readable = getReadableStreamSomehow();var readable = getReadableStreamSomehow();
readable.on('readable', function () {readable.on('readable', () => {
// there is some data to read now // there is some data to read now
});});
``````
@ -234,12 +234,12 @@ In the former case, `.read()` will return that data. In the latter case,
is an empty file:is an empty file:
```javascript```javascript
var fs = require('fs');const fs = require('fs');
var rr = fs.createReadStream('foo.txt');var rr = fs.createReadStream('foo.txt');
rr.on('readable', function () {rr.on('readable', () => {
console.log('readable:', rr.read()); console.log('readable:', rr.read());
});});
rr.on('end', function () {rr.on('end', () => {
console.log('end'); console.log('end');
});});
``````
@ -280,11 +280,11 @@ available will remain in the internal buffer.
```javascript```javascript
var readable = getReadableStreamSomehow();var readable = getReadableStreamSomehow();
readable.on('data', function (chunk) {readable.on('data', (chunk) => {
console.log('got %d bytes of data', chunk.length); console.log('got %d bytes of data', chunk.length);
readable.pause(); readable.pause();
console.log('there will be no more data for 1 second'); console.log('there will be no more data for 1 second');
setTimeout(function () { setTimeout(() => {
console.log('now data will start flowing again'); console.log('now data will start flowing again');
readable.resume(); readable.resume();
}, 1000); }, 1000);
@ -335,7 +335,7 @@ end.
```javascript```javascript
reader.pipe(writer, { end: false });reader.pipe(writer, { end: false });
reader.on('end', function () {reader.on('end', () => {
writer.end('Goodbye\n'); writer.end('Goodbye\n');
});});
``````
@ -366,7 +366,7 @@ drained.
```javascript```javascript
var readable = getReadableStreamSomehow();var readable = getReadableStreamSomehow();
readable.on('readable', function () {readable.on('readable', () => {
var chunk; var chunk;
while (null !== (chunk = readable.read())) { while (null !== (chunk = readable.read())) {
console.log('got %d bytes of data', chunk.length); console.log('got %d bytes of data', chunk.length);
@ -395,7 +395,7 @@ data.
```javascript```javascript
var readable = getReadableStreamSomehow();var readable = getReadableStreamSomehow();
readable.resume();readable.resume();
readable.on('end', function () {readable.on('end', () => {
console.log('got to the end, but did not read anything'); console.log('got to the end, but did not read anything');
});});
``````
@ -420,7 +420,7 @@ as strings, always use this method.
```javascript```javascript
var readable = getReadableStreamSomehow();var readable = getReadableStreamSomehow();
readable.setEncoding('utf8');readable.setEncoding('utf8');
readable.on('data', function (chunk) {readable.on('data', (chunk) => {
assert.equal(typeof chunk, 'string'); assert.equal(typeof chunk, 'string');
console.log('got %d characters of string data', chunk.length); console.log('got %d characters of string data', chunk.length);
});});
@ -443,7 +443,7 @@ var writable = fs.createWriteStream('file.txt');
// All the data from readable goes into 'file.txt',// All the data from readable goes into 'file.txt',
// but only for the first second// but only for the first second
readable.pipe(writable);readable.pipe(writable);
setTimeout(function () {setTimeout(() => {
console.log('stop writing to file.txt'); console.log('stop writing to file.txt');
readable.unpipe(writable); readable.unpipe(writable);
console.log('manually close the file stream'); console.log('manually close the file stream');
@ -471,7 +471,7 @@ for Stream Implementors, below.)
// Pull off a header delimited by \n\n// Pull off a header delimited by \n\n
// use unshift() if we get too much// use unshift() if we get too much
// Call the callback with (error, header, stream)// Call the callback with (error, header, stream)
var StringDecoder = require('string_decoder').StringDecoder;const StringDecoder = require('string_decoder').StringDecoder;
function parseHeader(stream, callback) {function parseHeader(stream, callback) {
stream.on('error', callback); stream.on('error', callback);
stream.on('readable', onReadable); stream.on('readable', onReadable);
@ -528,12 +528,12 @@ as a convenience for interacting with old Node.js programs and libraries.
For example:For example:
```javascript```javascript
var OldReader = require('./old-api-module.js').OldReader;const OldReader = require('./old-api-module.js').OldReader;
var oreader = new OldReader ;const Readable = require('stream').Readable ;
var Readable = require('stream').Readable ;const oreader = new OldReader ;
var myReader = new Readable().wrap(oreader);const myReader = new Readable().wrap(oreader);
myReader.on('readable', function () {myReader.on('readable', () => {
myReader.read(); // etc. myReader.read(); // etc.
});});
``````
@ -615,10 +615,10 @@ to the underlying system, this event is emitted.
```javascript```javascript
var writer = getWritableStreamSomehow();var writer = getWritableStreamSomehow();
for (var i = 0; i < 100 ; i + + ) { for (var i = 0; i < 100 ; i + + ) {
writer.write('hello, #' + i + ' !\n'); writer.write('hello, #${i} !\n');
}}
writer.end('this is the end\n');writer.end('this is the end\n');
writer.on('finish', function () {writer.on('finish', () => {
console.error('all writes are now complete.'); console.error('all writes are now complete.');
});});
``````
@ -633,7 +633,7 @@ stream, adding this writable to its set of destinations.
```javascript```javascript
var writer = getWritableStreamSomehow();var writer = getWritableStreamSomehow();
var reader = getReadableStreamSomehow();var reader = getReadableStreamSomehow();
writer.on('pipe', function (src) {writer.on('pipe', (src) => {
console.error('something is piping into the writer'); console.error('something is piping into the writer');
assert.equal(src, reader); assert.equal(src, reader);
});});
@ -650,7 +650,7 @@ readable stream, removing this writable from its set of destinations.
```javascript```javascript
var writer = getWritableStreamSomehow();var writer = getWritableStreamSomehow();
var reader = getReadableStreamSomehow();var reader = getReadableStreamSomehow();
writer.on('unpipe', function (src) {writer.on('unpipe', (src) => {
console.error('something has stopped piping into the writer'); console.error('something has stopped piping into the writer');
assert.equal(src, reader); assert.equal(src, reader);
});});
@ -955,8 +955,8 @@ This is a basic example of a Readable stream. It emits the numerals
from 1 to 1,000,000 in ascending order, and then ends.from 1 to 1,000,000 in ascending order, and then ends.
```javascript```javascript
var Readable = require('stream').Readable;const Readable = require('stream').Readable;
var util = require('util');const util = require('util');
util.inherits(Counter, Readable);util.inherits(Counter, Readable);
function Counter(opt) {function Counter(opt) {
@ -995,8 +995,8 @@ below for a better implementation.
// Using Readable directly for this is sub-optimal. See the// Using Readable directly for this is sub-optimal. See the
// alternative example below under the Transform section.// alternative example below under the Transform section.
var Readable = require('stream').Readable;const Readable = require('stream').Readable;
var util = require('util');const util = require('util');
util.inherits(SimpleProtocol, Readable);util.inherits(SimpleProtocol, Readable);
@ -1012,13 +1012,13 @@ function SimpleProtocol(source, options) {
this._source = source; this._source = source;
var self = this; var self = this;
source.on('end', function () { source.on('end', () => {
self.push(null); self.push(null);
}); });
// give it a kick whenever the source is readable // give it a kick whenever the source is readable
// read(0) will not consume any bytes // read(0) will not consume any bytes
source.on('readable', function () { source.on('readable', () => {
self.read(0); self.read(0);
}); });
@ -1210,8 +1210,8 @@ would be piped into the parser, which is a more idiomatic Node.js stream
approach.approach.
```javascript```javascript
var util = require('util');const util = require('util');
var Transform = require('stream').Transform;const Transform = require('stream').Transform;
util.inherits(SimpleProtocol, Transform);util.inherits(SimpleProtocol, Transform);
function SimpleProtocol(options) {function SimpleProtocol(options) {
@ -1518,10 +1518,10 @@ For example, consider the following code:
```javascript```javascript
// WARNING! BROKEN!// WARNING! BROKEN!
net.createServer(function (socket) {net.createServer((socket) => {
// we add an 'end' method, but never consume the data // we add an 'end' method, but never consume the data
socket.on('end', function () { socket.on('end', () => {
// It will never get here. // It will never get here.
socket.end('I got your message (but didnt read it)\n'); socket.end('I got your message (but didnt read it)\n');
}); });
@ -1538,9 +1538,9 @@ start the flow of data:
```javascript```javascript
// Workaround// Workaround
net.createServer(function (socket) {net.createServer((socket) => {
socket.on('end', function () { socket.on('end', () => {
socket.end('I got your message (but didnt read it)\n'); socket.end('I got your message (but didnt read it)\n');
}); });
@ -1589,9 +1589,9 @@ respectively. These options can be used to implement parsers and
serializers with Transform streams.serializers with Transform streams.
```javascript```javascript
var util = require('util');const util = require('util');
var StringDecoder = require('string_decoder').StringDecoder;const StringDecoder = require('string_decoder').StringDecoder;
var Transform = require('stream').Transform;const Transform = require('stream').Transform;
util.inherits(JSONParseStream, Transform);util.inherits(JSONParseStream, Transform);
// Gets \n-delimited JSON string data, and emits the parsed objects// Gets \n-delimited JSON string data, and emits the parsed objects
James M Snell
9 years ago