.is()

Syntax

.is(selector)

Parameters

selector: A string containing a selector expression to match elements against

Return value

A Boolean indicating whether an element matches the selector.

Description

Check the current matched set of elements against a selector and return true if at least one of these elements matches the selector.

 
<html>
  <head>
    <script src="http://java2s.com/Book/JavaScriptDemo/jQuery/jquery-1.8.0.min.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>

Click to view the demo

Is it a style I need.

 
<html>
  <head>
    <script src="http://java2s.com/Book/JavaScriptDemo/jQuery/jquery-1.8.0.min.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>

Click to view the demo

is(expr)

 
<html>
  <head>
    <script src="http://java2s.com/Book/JavaScriptDemo/jQuery/jquery-1.8.0.min.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>

Click to view the demo

is() can be used inside an event handler.

 
<html>
  <head>
    <script src="http://java2s.com/Book/JavaScriptDemo/jQuery/jquery-1.8.0.min.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>

Click to view the demo