<html> <body> <table id="myTable" border="1"> <tr id="myRow"> <td>Cell 1</td> <td>Cell 2</td> </tr> <tr> <td>Cell 3</td> <td>Cell 4</td> </tr> </table> <button onclick="alert(myTable.cells.length);">Length of table</button> <button onclick="alert(myRow.cells.length);">Length of row</button> </body> </html>