how to get the id of an element in javascript on click code example

Example 1: get id of clicked element javascript

<button id="3" onClick="reply_click(this.id)">B3</button>
    
<script type="text/javascript">
  function reply_click(clicked_id)
  {
      alert(clicked_id);
  }
</script>

Example 2: get id of element javascript

var element = document.getElementsByTagName("div")[0];
var id = element.id;