​x
 
<!DOCTYPE html>
<html>
<head>
<script>
function createCaption(id) {
  document.getElementById(id).createCaption().innerHTML = "我的新标题";
}
</script>
</head>
<body>
​
<table id="myTable" style="border: 1px solid black">
  <tr>
    <td>Row1 cell1</td>
    <td>Row1 cell2</td>
  </tr>
  <tr>
    <td>Row2 cell1</td>
    <td>Row2 cell2</td>
  </tr>
</table>
​
<p>
<input type="button" onclick="createCaption('myTable')" value="创建标题">
</p>
​
</body>
</html>
​