验证码倒计时方法

 

<input type="button" id="btn" value="免费获取验证码" onclick="settime(this)" />

var countdown = 60;
function settime(obj) {
    if (countdown == 0) {
        obj.removeAttribute("disabled");
        obj.value="免费获取验证码";
        countdown = 60;
        return;
    } else {
        obj.setAttribute("disabled", true);
        obj.value="重新发送(" + countdown + ")";
        countdown--;
    }
setTimeout(function() {
    settime(obj) }
    ,1000)
}