处理数组的forEach map filter的兼容性

1     //forEach处理
2     if(!Array.prototype.forEach) {
3         Array.prototype.forEach = function (callback) {
4             for(var i=0,len=this.length;i<len;i++) {
5                 callback(this[i], i);
6             }
7         }
8     }

 1     //处理map
 2     if(!Array.prototype.map) {
 3         Array.prototype.map = function (callback) {
 4             var arr = [];
 5             for(var i=0,len=this.length;i<len;i++) {
 6                 arr.push(callback(this[i], i));
 7             }
 8             return arr;
 9         }
10     }

 1     //处理filter
 2     if(!Array.prototype.filter) {
 3         Array.prototype.filter = function (callback) {
 4             var arr = [];
 5             for(var i=0,len=this.length;i<len;i++) {
 6                 if(callback(this[i], i)) {
 7                     arr.push(this[i])
 8                 }
 9             }
10             return arr;
11         }
12     }