Use given args instead of arguments object.

This speeds up argument access
when there are 1 or 2 event arguments.

Author: RubenVerborgh

lib/events.js

@@ -65,7 +65,7 @@ EventEmitter.prototype.setMaxListeners = function setMaxListeners(n) {
   return this;
 };
 
-EventEmitter.prototype.emit = function emit(type) {
+EventEmitter.prototype.emit = function emit(type, arg1, arg2) {
   var er, handler, len, args, i, listeners;
 
   if (!this._events)
@@ -97,28 +97,27 @@ EventEmitter.prototype.emit = function emit(type) {
   if (this.domain && this !== process)
     this.domain.enter();
 
+  len = arguments.length;
   if (util.isFunction(handler)) {
-    switch (arguments.length) {
+    switch (len) {
       // fast cases
       case 1:
         handler.call(this);
         break;
       case 2:
-        handler.call(this, arguments[1]);
+        handler.call(this, arg1);
         break;
       case 3:
-        handler.call(this, arguments[1], arguments[2]);
+        handler.call(this, arg1, arg2);
         break;
       // slower
       default:
-        len = arguments.length;
         args = new Array(len - 1);
         for (i = 1; i < len; i++)
           args[i - 1] = arguments[i];
         handler.apply(this, args);
     }
   } else if (util.isObject(handler)) {
-    len = arguments.length;
     args = new Array(len - 1);
     for (i = 1; i < len; i++)
       args[i - 1] = arguments[i];