<html><head><script>function changeBorder(id) { document.getElementById(id).style.border = "5px solid";}</script></head><body><table style="border:1px solid black" id="myTable"> <tr> <td>100</td> <td>200</td> </tr> <tr> <td>300</td> <td>400</td> </tr></table><p><input type="button" onclick="changeBorder('myTable')" value="更改边框"></p></body></html>