在线运行代码 - 菜鸟教程

<!DOCTYPE html>
<html>
<head> 
<meta charset="utf-8"> 
<title>菜鸟教程(cainiaoplay.com)</title>
<script>
function displayResult(){
	document.getElementById("myHeader1").colSpan="2";
}
</script>
</head>
<body>

<table border="1">
	<tr>
		<th id="myHeader1">月份</th>
		<th id="myHeader2">存款</th>
	</tr>
	<tr>
		<td>January</td>
		<td>$100.00</td>
  	</tr>
  	<tr>
		<td>February</td>
		<td>$10.00</td>
  	</tr>
  	<tr>
		<td>March</td>
		<td>$80.00</td>
  	</tr>
</table>
<br> 
<button type="button" onclick="displayResult()">改变第一个单元格的横跨列数</button>

</body>
</html>
源代码

动行结果
