JS - 按钮倒计时

<input type="button" id="btn" value="点击获取效验码" />

	//倒计时
	var wait=60;
	function time(o) {
        if (wait == 0) {
            o.removeAttribute("disabled");          
            o.value="点击获取效验码";
            wait = 60;
        } else {
            o.setAttribute("disabled", true);
            o.value="重新发送(" + wait + ")";
            wait--;
            setTimeout(function() {
                time(o)
            },
            1000)
        }
    }
	//调用
	time(this);