dgram: change parameter name in set(Multicast)TTL

Changed the parameter name in set(Multicast)TTL from "arg" to "ttl"
both within code and error messages and added the actual type of the
argument to the error message.

PR-URL: https://github.com/nodejs/node/pull/13747
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

lib/dgram.js

@@ -524,35 +524,31 @@ Socket.prototype.setBroadcast = function(arg) {
 };
 
 
-Socket.prototype.setTTL = function(arg) {
-  if (typeof arg !== 'number') {
-    throw new errors.TypeError('ERR_INVALID_ARG_TYPE',
-                               'arg',
-                               'number');
+Socket.prototype.setTTL = function(ttl) {
+  if (typeof ttl !== 'number') {
+    throw new errors.TypeError('ERR_INVALID_ARG_TYPE', 'ttl', 'number', ttl);
   }
 
-  var err = this._handle.setTTL(arg);
+  var err = this._handle.setTTL(ttl);
   if (err) {
     throw errnoException(err, 'setTTL');
   }
 
-  return arg;
+  return ttl;
 };
 
 
-Socket.prototype.setMulticastTTL = function(arg) {
-  if (typeof arg !== 'number') {
-    throw new errors.TypeError('ERR_INVALID_ARG_TYPE',
-                               'arg',
-                               'number');
+Socket.prototype.setMulticastTTL = function(ttl) {
+  if (typeof ttl !== 'number') {
+    throw new errors.TypeError('ERR_INVALID_ARG_TYPE', 'ttl', 'number', ttl);
   }
 
-  var err = this._handle.setMulticastTTL(arg);
+  var err = this._handle.setMulticastTTL(ttl);
   if (err) {
     throw errnoException(err, 'setMulticastTTL');
   }
 
-  return arg;
+  return ttl;
 };
 
 

test/parallel/test-dgram-multicast-setTTL.js

@@ -40,7 +40,7 @@ socket.on('listening', common.mustCall(() => {
   }, common.expectsError({
     code: 'ERR_INVALID_ARG_TYPE',
     type: TypeError,
-    message: /^The "arg" argument must be of type number$/
+    message: 'The "ttl" argument must be of type number. Received type string'
   }));
 
   //close the socket

test/parallel/test-dgram-setTTL.js

@@ -14,7 +14,7 @@ socket.on('listening', common.mustCall(() => {
   }, common.expectsError({
     code: 'ERR_INVALID_ARG_TYPE',
     type: TypeError,
-    message: /^The "arg" argument must be of type number$/
+    message: 'The "ttl" argument must be of type number. Received type string'
   }));
 
   // TTL must be a number from > 0 to < 256