Is it the first child : Selector children « jQuery « JavaScript Tutorial

<html>
  <head>
    <script type="text/javascript" src="js/jquery-1.3.2.js"></script>
    <script type="text/javascript">
        $(document).ready(function(){
           $("div").one('click', function () {
              if ($(this).is(":first-child")) {
                $("p").text("It's the first div.");
              }else{
                $("p").text("It's NOT the first div.");
              }
              $("p").hide().slideDown("slow");
              
           });
        });
    </script>
     <style>
     div { border:2px white solid;}
  </style>

  </head>
  <body>
    <body>
      Press each to see the text.
      <div>asdf</div>
      <div>asdf</div>
      <div>asdf</div>
      <div>asdf</div>
      <div>asdf</div>
      <div>asdf</div>
      <p></p>
  </body>
</html>

30.4.Selector children
	30.4.1.	nthChild(index)
	30.4.2.	onlyChild(): If the parent has other child elements, nothing is matched.
	30.4.3.	Select n-th child
	30.4.4.	Finds all children of the element with id "main"
	30.4.5.	Finds all p elements that are children of a div element
	30.4.6.	Is it the first child
	30.4.7.	Matches all child elements specified by child of elements specified by parent