验证码倒计时

htm：

<input type="button" value="获取" onclick="settime(this)"/>

js：

var countdown=60;
function settime(val) {
    if (countdown == 0) {
        val.removeAttribute("disabled");
        val.value="再次获取";
        countdown = 60;
        return
    } else {
        val.setAttribute("disabled", true);
        val.value="重新发送(" + countdown + ")";
        countdown--;
    }
    setTimeout(function() {
        settime(val)
    },1000)
}