[perf] micro-optimisations (socketio#2793)

Author: billouboq

lib/socket.js

@@ -141,13 +141,14 @@ Socket.prototype.emit = function(ev){
     emit.apply(this, arguments);
   } else {
     var args = Array.prototype.slice.call(arguments);
-    var packet = {};
-    packet.type = hasBin(args) ? parser.BINARY_EVENT : parser.EVENT;
-    packet.data = args;
+    var packet = {
+      type: hasBin(args) ? parser.BINARY_EVENT : parser.EVENT,
+      data: args
+    };
     var flags = this.flags || {};
 
     // access last argument to see if it's an ACK callback
-    if ('function' == typeof args[args.length - 1]) {
+    if (typeof args[args.length - 1] === 'function') {
       if (this._rooms || flags.broadcast) {
         throw new Error('Callbacks are not supported when broadcasting');
       }
@@ -495,15 +496,16 @@ Socket.prototype.compress = function(compress){
 Socket.prototype.dispatch = function(event){
   debug('dispatching an event %j', event);
   var self = this;
-  this.run(event, function(err){
+  function dispatchSocket(err) {
     process.nextTick(function(){
       if (err) {
         return self.error(err.data || err.message);
       }
       emit.apply(self, event);
     });
-  });
-}
+  }
+  this.run(event, dispatchSocket);
+};
 
 /**
  * Sets up socket middleware.