                        課程
                    
                        /前端開發
                        
                            /JavaScript
                        
                        /Tab選項卡切換效果

怎么不能實現呢

<!doctype html>
<html>
<head>
??? <meta charset="UTF-8">
?<title>Document</title>
??? <style>
??????? #receive{display:none;}
???????
??? </style>
?<script type="text/javascript">
?window.onload=function(){
???? var send=document.getElementById('send'),
??????????? receive=document.getElementById('receive'),
???????? times=60,
???????? timer=null;
???? send.onclick=function(){
?????? // 計時開始
????????? timer=setInterval('showTime',500);????????
???? }
??????? function showTime(){
??????????? if(times>=0){
????????????? receive.style.display='block';
??????????????? receive.disabled ='false';
??????????????? receive.value=times+'秒后重試';
??????????????? times--;
????send.disabled='false';
??????????? }
??????????? else{????
????clearInterval(timer);
????? receive.style.display='none';
??????????? }
??????? }
?}
?</script>
</head>
<body>
?<input type="button" id="send" value="發送驗證碼" >
??? <input type="button" id="receive" >
</body>
</html>