js倒计时

点击button时调用settime(60);

    function settime(countdown)     {         if (countdown == 0)         {             document.getElementById('idSend').disabled = false;                document.getElementById('idSend').innerHTML = "获取验证码(60s)";             // alert(countdown);        }        else        {             // alert(countdown);            document.getElementById('idSend').disabled = true;                document.getElementById('idSend').innerHTML = "重新发送("+countdown+"s)";             countdown--;             setTimeout(function() {                 settime(countdown); //1s timeout调用            },1000)         }    }