JavaScript Tutorial/jQuery/is

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is() can be used inside an event handler.

<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")) {
                        $("p").text(":first-child");
                      } else if ($(this).is(".blue,.red")) {
                        $("p").text("It"s a blue or red div.");
                      } else if ($(this).is(":contains("asdf")")) {
                        $("p").text("It"s asdf!");
                      } else {
                        $("p").html("It"s nothing <em>special</em>.");
                      }
                    });
                    
        });
    </script>
 <style>
  div.middle { color: red; }
  
</style>
  </head>
  <body>
    <body>
          <div>asdf</div>
          <div class="blue">asdf</div>
          <div class="red">asdf</div>
          <div><span>asdf</span>asdf</div>
          <div class="blue">asdf</div>
          <p>asdf</p>
    </body>
</html>


is(expr)

<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")) {
                        $("p").text(":first-child");
                      } else if ($(this).is(".blue,.red")) {
                        $("p").text("It"s a blue or red div.");
                      } else if ($(this).is(":contains("asdf")")) {
                        $("p").text("It"s asdf!");
                      } else {
                        $("p").html("It"s nothing <em>special</em>.");
                      }
                    });
                    
        });
    </script>
 <style>
  div.middle { color: red; }
  
</style>
  </head>
  <body>
    <body>
          <div>asdf</div>
          <div class="blue">asdf</div>
          <div class="red">asdf</div>
          <div><span>asdf</span>asdf</div>
          <div class="blue">asdf</div>
          <p>asdf</p>
    </body>
</html>


Is it class

<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(".blue,.red")) {
                $("p").text("It"s the blue and red div.");
              }else{
                $("p").text("It"s NOT the blue and red div.");
              }
              $("p").hide().slideDown("slow");
              
           });
        });
    </script>
  </head>
  <body>
    <body>
      Press each to see the text.
      <div class=blue>asdf</div>
      <div class=red>asdf</div>
      <div>asdf</div>
      <div>asdf</div>
      <div>asdf</div>
      <div>asdf</div>
      <p></p>
  </body>
</html>


Traversing IS

<html>
  <head>
    <script type="text/javascript" src="js/jquery-1.3.2.js"></script>
    <script type="text/javascript">
        $(document).ready(function(){
            var isFormParent = $("input[type="checkbox"]").parent().is("form")
            alert(isFormParent);
        });
    </script>
  </head>
  <body>
    <body>
      <form><input type="checkbox" /></form>
      <div></div>
  </body>
</html>