重写默认方法兼容ie， 比如filter，keys等

重写 Object.keys, Array.prototype.map, Array.prototype.filter, Array.prototype.reduce， 使其适合ie

1. keys

Object.myKeys = function (params) {
    var ary = [];
    if (Object.keys) {
        ary = this.keys(params);
    } else {
        for(var key in params ) if(hasOwn.call(params,key)){
            ary.push(key) ;
        }
        var DONT_ENUM =  "propertyIsEnumerable,isPrototypeOf,hasOwnProperty,toLocaleString,toString,valueOf,constructor".split(","),
            hasOwn = ({}).hasOwnProperty;
        for (var i in {
            toString: 1
        }){
            DONT_ENUM = false;
        }
        if(DONT_ENUM && params){
            for(var i = 0 ;key = DONT_ENUM[i++]; ){
                if(hasOwn.call(params,key)){
                    ary.push(key);
                }
            }
        }
    }
    return ary;
}

2.使ie 支持map

Array.prototype.myMap = function (fn, context) {
    context = context || window;
    var ary = [];
    if (Array.prototype.map) {
        ary = this.map(fn, context);
    } else {
        for (var i = 0; i < this.length; i++) {
            ary[i] = fn.apply(context, [this[i], i, this]);
        }
    }
    return ary;
}

3. filter

Array.prototype.myFilter = function (fn) {
    var ary = [];
    if (Array.prototype.filter) {
        ary = this.filter(fn);
    } else {
        if (this === void 0 || this === null) {
            throw new TypeError();
        }
        var t = Object(this);
        var len = t.length >>> 0;
        if (typeof fn !== "function")
          throw new TypeError();

        var thisArg = arguments.length >= 2 ? arguments[1] : void 0;
        for (var i = 0; i < len; i++)
        {
          if (i in t)
          {
            var val = t[i];
            if (fn.call(thisArg, val, i, t))
              ary.push(val);
          }
        }
    }
    return ary;
}

4. refuce

Array.prototype.myReduce = function (callback, opt_initialValue) {
    var value = '';
    if (Array.prototype.reduce) {
        value = this.reduce(callback, opt_initialValue);
    } else {
        if (this === void 0 || this === null) {
          throw new TypeError();
        }
        var index,
            length = this.length >>> 0,
            isValueSet = false;
        if (1 < arguments.length) {
          value = opt_initialValue;
          isValueSet = true;
        }
        for (index = 0; length > index; ++index) {
          if (this.hasOwnProperty(index)) {
            if (isValueSet) {
              value = callback(value, this[index], index, this);
            }
            else {
              value = this[index];
              isValueSet = true;
            }
          }
        }
        if (!isValueSet) {
            value = '';
            //throw new TypeError('Reduce of empty array with no initial value');
        }
    }
    return value;
}