為什么會報錯？document.getElementById('count').value=num;這句話不對？
<!DOCTYPE?HTML>
<html>
<head>
<meta?http-equiv="Content-Type"?content="text/html;?charset=utf-8">
<title>計時器</title>
<script?type="text/javascript">
??var?num=0;
??function?startCount()?{????
??document.getElementById('count').value=num;????
??num=num+1;????
??setTimeout("startCount()",1000);??
??}??
??startCount();
</script>
</head>
<body>
<form>
<input?type="text"?id="count"?/>
</form>
</body>
</html>VM1245:4 Uncaught TypeError: Cannot set property 'value' of null
? ? at startCount (<anonymous>:4:43)
? ? at <anonymous>:8:3
? ? at g (ceditor.js?v=201807191446:1)
? ? at v.runCode (ceditor.js?v=201807191446:1)
? ? at Object.success (ceditor.js?v=201807191446:1)
? ? at c (jquery.js?v=201807191446:2)
? ? at Object.fireWith [as resolveWith] (jquery.js?v=201807191446:2)
? ? at k (jquery.js?v=201807191446:4)
? ? at XMLHttpRequest.r (jquery.js?v=201807191446:4)
2018-08-10
你這個 input標簽里面連 ?調用函數都沒有 當然沒東西了
2018-07-20
是不是把13行去掉，18行后面插入<input type="button" value="Start" onClick="startCount()">