                        课程
                    
                        /前端开发
                        
                            /JavaScript
                        
                        /JavaScript进阶篇

用setInterval完成倒计时

<body onload="timerb()">  
    <h3>操作成功</h3>  
    <p id="p1"></p>  
    <script>    
        var num = 5;    
        var timer = null;    
        function timerb() {      
            document.getElementById('p1').innerHTML = num + '秒后跳到首页'      
            num--;      
            if (!timer) {        
                timer = setInterval("timerb()", 1000)     
             }      
            if (num === 0) { 
               timer = null;        
               location.replace('http://www.baidu.com')     
            }    
        } 
     </script>
</body>