added 'addEventListener'

Author: Rob Griffiths

lib/XMLHttpRequest.js

@@ -128,7 +128,7 @@ exports.XMLHttpRequest = function() {
   /**
    * Gets all the response headers.
    *
-   * @return string 
+   * @return string
    */
   this.getAllResponseHeaders = function() {
     if (this.readyState < this.HEADERS_RECEIVED || errorFlag) {
@@ -349,6 +349,14 @@ exports.XMLHttpRequest = function() {
     this.readyState = this.UNSENT;
   };
 
+  var listeners = {};
+  this.addEventListener = function(event, callback) {
+    if (!(event in listeners)) {
+      listeners[event] = [];
+    }
+    listeners[event].push(callback);
+  };
+
   /**
    * Changes readyState and calls onreadystatechange.
    *
@@ -359,5 +367,12 @@ exports.XMLHttpRequest = function() {
     if (typeof self.onreadystatechange === "function") {
       self.onreadystatechange();
     }
+
+    if ("readystatechange" in listeners) {
+      var count = listeners["readystatechange"].length, i = 0;
+      for(; i < count; i++) {
+        listeners["readystatechange"][i].call(self);
+      }
+    }
   };
 };