IE浏览器不兼容indexOf问题

1if (!Array.prototype.indexOf) {
2    Array.prototype.indexOf = function (elt /*, from*/) {
3        var len = this.length >>> 0;
4        var from = Number(arguments[1]) || 0;
5        from = (from < 0)
6             ? Math.ceil(from)
7             : Math.floor(from);
8        if (from < 0)
9            from += len;
10        for (; from < len; from++) {
11            if (from in this &&
12                this[from] === elt)
13                return from;
14        }
15        return -1;
16    };
17}

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;    };}