把一下代碼放在你的indexOf方法的上面：

  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;
    };
  }