ie不支持indexOf解决办法

        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;
          };
        }

把这段代码插入到indexOf上面