javascript解决IE8不支持filter的方法

if (!Array.prototype.filter)
{
 Array.prototype.filter = function(fun /*, thisArg */)
 {
 "use strict";

 if (this === void 0 || this === null)
 throw new TypeError();

 var t = Object(this);
 var len = t.length >>> 0;
 if (typeof fun !== "function")
 throw new TypeError();

 var res = [];
 var thisArg = arguments.length >= 2 ? arguments[1] : void 0;
 for (var i = 0; i < len; i++)
 {
 if (i in t)
 {
 var val = t[i];

 // NOTE: Technically this should Object.defineProperty at
 // the next index, as push can be affected by
 // properties on Object.prototype and Array.prototype.
 // But that method's new, and collisions should be
 // rare, so use the more-compatible alternative.
 if (fun.call(thisArg, val, i, t))
 res.push(val);
 }
 }

 return res;
 };
}