var Iterator = function (fn) {             var coroutine = null;             var cofn_this = null;             var yield = function() {                 coroutine.apply(cofn_this, arguments);             }             // support IE.             // NOTE: IE eval("function(){}") does not return a function object.             eval('fn = ' + fn.toString());             return function(cofn, cothis){                 coroutine = cofn;                 cofn_this = cothis;                 return fn.apply(this)             };         }         Array.prototype.forEach = new Iterator(function () {             for (var i = 0; i < this.length; i ++) {                 yield(this[i])             }         });         // example.         this.display = window.alert;         var A = [1,2,3,4,5];         A.forEach(function(it){             this.display(it)         }, this);