<table width="100%" border="1" cellspacing="0" cellpadding="0" id="example_table"> 
  <tr> 
    <td> </td> 
    <td> </td> 
    <td> </td> 
    <td> </td> 
    <td> </td> 
  </tr> 
  <tr> 
    <td> </td> 
    <td> </td> 
    <td> </td> 
    <td> </td> 
    <td> </td> 
  </tr> 
  <tr> 
    <td> </td> 
    <td> </td> 
    <td> </td> 
    <td> </td> 
    <td> </td> 
  </tr> 
</table> 

//表格行数 
var rows = document.getElementById("example_table").rows.length; 
 
//表格列数 
var cells = document.getElementById("example_table").rows.item(0).cells.length;