JS实现自动倒计时

时间：2023-02-13 10:02:04
<!DOCTYPE html>

<html>

<head>

<meta charset="utf-8">

<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1">

<title>JS实现自动倒计时30秒后按钮才可用</title>

<meta name="keywords" content="javascript,倒计时" />

<meta name="description" content="" />

<style>

.demo{width:300px; margin:60px auto 10px auto}

@media only screen and (min-width: 420px) {

	.demo{width:500px; margin:60px auto 10px auto}

}

.demo p{line-height:36px}

.button {

	display: inline-block;

	cursor:pointer;

	outline: none;

	text-align: center;

	text-decoration: none;

	font: 16px/100% 'Microsoft yahei',Arial, Helvetica, sans-serif;

	padding: .5em 2em .55em;

	-webkit-border-radius: .5em;

	-moz-border-radius: .5em;

	border-radius: .5em;

	color: #606060;

	border: solid 1px #b7b7b7;

	background: #ededed;

}

.button:hover {

	text-decoration: none;

	background: #fff;

}

.button:active {

	position: relative;

	top: 1px;

	color: #999;

}

</style>

</head>

<body>

<div id="header">

   <div id="logo"><h1><a href="" title=""></a></h1></div>

</div>

<div id="main">

	<h2 class="top_title"><a href=""></a></h2>

	<div class="demo">

	<p>示例一：要求用户阅读完条款内容才能激活按钮</p>

	<form action="" method="post" name="agree">

		<input type="submit" class="button" value="请认真查看<服务条款和声明> (30)" id="agree_btn" name="agreeb">

	</form>

	<br/>

	<br/>

	<br/>

	<p>示例二：要求用户激活短信通道向用户手机发送验证码</p>

	<form action="" method="post" name="myform">

		<input type="button" class="button" value="获取手机验证码"  id="phone_btn" name="phone" onclick="showtime(30)">

	</form>

	</div>

</div>

<script>

var secs = 30;

document.agree.agreeb.disabled=true;

for(var i=1;i<=secs;i++) {

	window.setTimeout("update(" + i + ")", i * 1000);

}

function update(num) {

	if(num == secs) {

		document.agree.agreeb.value =" 我 同 意 ";

		document.agree.agreeb.disabled=false;

	}

	else {

		var printnr = secs-num;

		document.agree.agreeb.value = "请认真查看<服务条款和声明> (" + printnr +")";

	}

}

function showtime(t){

	document.myform.phone.disabled=true;

	for(i=1;i<=t;i++) {

		window.setTimeout("update_p(" + i + ","+t+")", i * 1000);

	}

}

function update_p(num,t) {

	if(num == t) {

		document.myform.phone.value =" 重新发送 ";

		document.myform.phone.disabled=false;

	}

	else {

		printnr = t-num;

		document.myform.phone.value = " (" + printnr +")秒后重新发送";

	}

}

</script>

<div id="footer">

</div>

</body>

</html>

　　

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