added Array.prototype.lastIndexOf

core.js

@@ -21,15 +21,14 @@
 
     /***********************************************************************
         Global Javascript objects
-    ************************************************************************/
 
-    /* Workarounds for browsers which do not natively support some ECMA
-     * standards.
-     *
-     * Although extending the DOM is a very bad idea and considered "evil",
-     * adding missing methods to global javascript objects is perfectly 
-     * acceptable.
-     */
+        Workarounds for browsers which do not natively support some ECMA
+        standards.
+
+        Although extending the DOM is a very bad idea and considered "evil",
+        adding missing methods to global javascript objects is perfectly
+        acceptable.
+    ************************************************************************/
 
     /* This is taken from https://developer.mozilla.org and is exactly the
      * one specified in ECMA-262.
@@ -38,15 +37,20 @@
     if (!Array.prototype.indexOf) {  
         Array.prototype.indexOf = function (searchElement /*, fromIndex */ ) {
             "use strict";
+
             if (this == null) {
                 throw new TypeError();
             }
+
             var t = Object(this);
             var len = t.length >>> 0;
+
             if (len === 0) {
                 return -1;
             }
+
             var n = 0;
+
             if (arguments.length > 0) {
                 n = Number(arguments[1]);
                 if (n != n) { // shortcut for verifying if it's NaN
@@ -55,17 +59,63 @@
                     n = (n > 0 || -1) * Math.floor(Math.abs(n));
                 }
             }
+
             if (n >= len) {
                 return -1;
             }
+
             var k = n >= 0 ? n : Math.max(len - Math.abs(n), 0);
+
             for (; k < len; k++) {
                 if (k in t && t[k] === searchElement) {
                     return k;
                 }
             }
+
+            return -1;
+        }
+    }
+
+    /* This is taken from https://developer.mozilla.org and is exactly the
+     * one specified in ECMA-262.
+     */
+
+    if (!Array.prototype.lastIndexOf) {
+        Array.prototype.lastIndexOf = function(searchElement /*, fromIndex*/) {
+        "use strict";
+
+        if (this == null) {
+            throw new TypeError();
+        }
+
+        var t = Object(this);
+        var len = t.length >>> 0;
+
+        if (len === 0) {
             return -1;
         }
+
+        var n = len;
+
+        if (arguments.length > 1) {
+            n = Number(arguments[1]);
+            if (n != n) {
+                n = 0;
+            } else if (n != 0 && n != (1 / 0) && n != -(1 / 0)) {
+                n = (n > 0 || -1) * Math.floor(Math.abs(n));
+            }
+        }
+
+        var k = n >= 0 ? Math.min(n, len - 1) : len - Math.abs(n);
+
+        for (; k >= 0; k--) {
+            if (k in t && t[k] === searchElement) {
+                return k;
+            }
+        }
+
+        return -1;
+      };
     }