CODE EXAMPLE FOR JAVASCRIPT

jquery select by id

<p id="test" class="hello">Hello</p>

<script>
  //Hide all html elements "p"
  $("p").hide();
  //Hide id="Test"
  $("#test").hide();
  //Hide all class="hello"
  $(".hello").hide();
  //Hide all "p" with class="hello"
  $("p.test").hide();
</script>