<html>
<head>
<script>
function createCaption()
{
var x=document.getElementById('myTable').createCaption();
x.innerHTML="My table caption";
}
</script>
</head>
<body>
<table id="myTable" border="1">
<tr>
<td>Row1 cell1</td>
<td>Row1 cell2</td>
</tr>
<tr>
<td>Row2 cell1</td>
<td>Row2 cell2</td>
</tr>
</table>
<br>
<input type="button" onclick="createCaption()" value="Create caption">
</body>
</html>