JavaScript实现按钮倒计时后自动跳转页面的完整代码

<a class="backUpPage" href="javascript:void(0);" rel="external nofollow" ><span></span>秒后 返回</a>

$(function () {
    var time = 5
    $('.backUpPage span').html(time)
	var timeFn = setInterval(function(){
	    time--
        $('.backUpPage span').html(time)
        if(time==0){
            clearTimeout(timeFn)
            window.location = 'http://www.baidu.com/'
        }
    },1000)	
})

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <button>点我跳转</button>
    <div></div>
    <script>
        var div=document.querySelector('div')
        var btn=document.querySelector('button')
        btn.addEventListener('click',function () {
            var timeer = 5
            btn.disabled=true
            x()
            setInterval(x,1000)
            function x() {
                if (timeer == 0) {
                    btn.disabled=false
                    location.href = 'http://www.baidu.com'
                } else {
                    btn.innerHTML = '还剩' + timeer + '秒'
                    div.innerHTML = '宁再' + timeer + '秒跳转'
                    timeer--
                }
            }
        })
    </script>
</body>
</html>