onclick alert clicked element

1<button id="1" onClick="reply_click(this.id)">B1</button>
2<button id="2" onClick="reply_click(this.id)">B2</button>
3<button id="3" onClick="reply_click(this.id)">B3</button>
4    
5<script type="text/javascript">
6  function reply_click(clicked_id)
7  {
8      alert(clicked_id);
9  }
10</script>