if (!Array.prototype.indexOf) {

     Array.prototype.indexOf = function(elt /*, from*/ ) {

         var len = this.length >>> 0;

         var from = Number(arguments[1]) || 0;

         from = (from < 0) ? Math.ceil(from) : Math.floor(from);

         if (from < 0)

             from += len;

         for (; from < len; from++) {

             if (from in this &&

                 this[from] === elt)

                 return from;

         }

         return -1;

     };

 }