console 命令行工具 X clear
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<html>

<head>
	<script type="text/javascript">
		function insCell(){
        {
        var x=document.getElementById('tr2').insertCell(0)
        x.innerHTML="John"
        }}
	</script>
	<style type="text/css">
		tr:hover,
		tr.altrow {
			background: #c4e4ff;
		}
	</style>
</head>

<body>

	<table border="1">
		<tr id="tr1">
			<th>Firstname</th>
			<th>Lastname</th>
		</tr>
		<tr id="tr2">
			<td>Peter</td>
			<td>Griffin</td>
		</tr>
	</table>
	<br />
<input type="button" onclick="insCell()" value="Insert cell">

</body>
</html>