原生JS 的60秒倒计时！

<!DOCTYPE html>
<html>
<head>
    <meta http-equiv="content-type" content="text/html; charset=UTF-8">
    <meta content="width=device-width,initial-scale=1.0,maximum-scale=1.0,user-scalable=no" id="viewport" name="viewport">
    <title>原生js60s倒计时</title>
    <style>
    </style>
</head>
<body>
<input type="button" id="btn" value="免费获取验证码" />
<script type="text/javascript">
    //发送验证码按钮的60s倒计时
var countdown = 60;
var mfbtn=document.getElementById(\'btn\');
var mfbtn=document.getElementById(\'btn\');
mfbtn.style.background=\'#0af\';
mfbtn.style.border=\'none\';
mfbtn.style.borderRadius=\'5px\';
mfbtn.style.height=\'30px\';
mfbtn.style.color=\'#fff\';
function settime(obj) {
        if (countdown == 0) {
            obj.disabled=false;
obj.value="免费获取验证码";
countdown = 60;
return;
} else {
            obj.disabled=true
obj.value="重新发送" + countdown
            countdown--;
mfbtn.style.background=\'#999\';
}
        setTimeout(function() {
            settime(obj);
}, 1000)
    };

mfbtn.onclick=function () {
        settime(mfbtn);
};

</script>
</body>
</html>