Optimize arguments usage

Fixes #263

Author: brycekahle

lib/event/emitter.js

@@ -34,12 +34,18 @@ EventEmitter.prototype.once = function(type, listener) {
   this.on(type, g);
 };
 
-EventEmitter.prototype.emit = function(type) {
+EventEmitter.prototype.emit = function() {
+  var type = arguments[0];
   var listeners = this._listeners[type];
   if (!listeners) {
     return;
   }
-  var args = Array.prototype.slice.call(arguments, 1);
+  // equivalent of Array.prototype.slice.call(arguments, 1);
+  var l = arguments.length;
+  var args = new Array(l - 1);
+  for (var ai = 1; ai < l; ai++) {
+    args[ai - 1] = arguments[ai];
+  }
   for (var i = 0; i < listeners.length; i++) {
     listeners[i].apply(this, args);
   }

lib/event/eventtarget.js

@@ -38,9 +38,11 @@ EventTarget.prototype.removeEventListener = function(eventType, listener) {
   }
 };
 
-EventTarget.prototype.dispatchEvent = function(event) {
+EventTarget.prototype.dispatchEvent = function() {
+  var event = arguments[0];
   var t = event.type;
-  var args = Array.prototype.slice.call(arguments, 0);
+  // equivalent of Array.prototype.slice.call(arguments, 0);
+  var args = arguments.length === 1 ? [event] : Array.apply(null, arguments);
   // TODO: This doesn't match the real behavior; per spec, onfoo get
   // their place in line from the /first/ time they're set from
   // non-null. Although WebKit bumps it to the end every time it's