为Array 添加indexOf

为array赋予属性

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;
    };
}

调用

var arrList = [];
if (arrList.indexOf(strID)== -1)
{
     //做爱做的事
}