net: refactor self=this to arrow functions

Refactor unused self=this code to code without without this pattern
making it more consistent with the rest of our code.

PR-URL: #5857
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Roman Klauke <romankl@users.noreply.github.com>

lib/net.js

@@ -444,9 +444,7 @@ Socket.prototype.destroySoon = function() {
 Socket.prototype._destroy = function(exception, cb) {
   debug('destroy');
 
-  var self = this;
-
-  function fireErrorCallbacks() {
+  function fireErrorCallbacks(self) {
     if (cb) cb(exception);
     if (exception && !self._writableState.errorEmitted) {
       process.nextTick(emitErrorNT, self, exception);
@@ -456,11 +454,11 @@ Socket.prototype._destroy = function(exception, cb) {
 
   if (this.destroyed) {
     debug('already destroyed, fire error callbacks');
-    fireErrorCallbacks();
+    fireErrorCallbacks(this);
     return;
   }
 
-  self._connecting = false;
+  this._connecting = false;
 
   this.readable = this.writable = false;
 
@@ -472,9 +470,9 @@ Socket.prototype._destroy = function(exception, cb) {
     if (this !== process.stderr)
       debug('close handle');
     var isException = exception ? true : false;
-    this._handle.close(function() {
+    this._handle.close(() => {
       debug('emit close');
-      self.emit('close', isException);
+      this.emit('close', isException);
     });
     this._handle.onread = noop;
     this._handle = null;
@@ -485,7 +483,7 @@ Socket.prototype._destroy = function(exception, cb) {
   // to make it re-entrance safe in case Socket.prototype.destroy()
   // is called within callbacks
   this.destroyed = true;
-  fireErrorCallbacks();
+  fireErrorCallbacks(this);
 
   if (this._server) {
     COUNTER_NET_SERVER_CONNECTION_CLOSE(this);
@@ -1078,33 +1076,31 @@ function Server(options, connectionListener) {
 
   EventEmitter.call(this);
 
-  var self = this;
-
   if (typeof options === 'function') {
     connectionListener = options;
     options = {};
-    self.on('connection', connectionListener);
+    this.on('connection', connectionListener);
   } else {
     options = options || {};
 
     if (typeof connectionListener === 'function') {
-      self.on('connection', connectionListener);
+      this.on('connection', connectionListener);
     }
   }
 
   this._connections = 0;
 
   Object.defineProperty(this, 'connections', {
-    get: internalUtil.deprecate(function() {
+    get: internalUtil.deprecate(() => {
 
-      if (self._usingSlaves) {
+      if (this._usingSlaves) {
         return null;
       }
-      return self._connections;
+      return this._connections;
     }, 'Server.connections property is deprecated. ' +
        'Use Server.getConnections method instead.'),
-    set: internalUtil.deprecate(function(val) {
-      return (self._connections = val);
+    set: internalUtil.deprecate((val) => {
+      return (this._connections = val);
     }, 'Server.connections property is deprecated.'),
     configurable: true, enumerable: false
   });