Como saber si un elemento posee una determinada clase: is('.class'), hasClass('class'), ver los comentarios

is('.class'), hasClass('class'), ver los comentarios

by limd

HTML

<html>
    <head>
        <link href='https://fonts.googleapis.com/css?family=Droid+Sans' rel='stylesheet' type='text/css'>

    </head>
    <body>
        <h1>Selecting in jQuery</h1>
        
        <h2><span class="plus">+</span> you can select by a filter as well <b>$(':hidden')</b></h2>
        <p>It is not necessary to provide an actual element in conjunction with a filter, such as
$('div:hidden'). It is possible to simply pass the filter alone, anywhere a selector expression is
            expected.</p>
        
        <a title="jQuery">jQuery.com</a>
<a href="http://www.jquery.com" title="jQuery" class="foo">jQuery.com</div>
<a href="">jQuery.com</a>
<a href="http://www.jquery.com" title="jQuery">jQuery.com</div>
    
    <div class="work-area">
        <div id="i0">jQuery</div>
        <div id="i1">jQuery</div>
    </div>
    </body>
    
    
    
</html>

CSS

body {
    line-height: 20px;
    padding: 10px;
    font-family: 'Droid Sans', sans-serif;
    font-size: 13px;
}

h1 {
    font-size: 16px;
    text-align: center;
    margin: 10px;
    padding: 10px;
}

h2 {
    font-size: 14px;
}

p {
    padding-left: 50px;
    font-size: 13px;
}


.work-area {
    border-left: 3px solid #66a3d2;
    padding: 10px; 
    margin: 10px;
}

.plus {
    color: #66a3d2;    
    font-size: 18px;    
}

JavaScript

jQuery(document).ready(function() {
    // Returns true
    console.log($('div').is('#i1'));
    // Returns false. Wrapper set contains no <div> with id="i2"
    console.log($('div').is('#i2'));
    // Returns false. Wrapper set contains no hidden <div>
    console.log($('div').is(':hidden'));

/*Some developers use is('.class') to determine if an element has a specific class, don't forget that jQuery
already has a method for doing this called hasClass('class') which can be used on elements that contain more
than one class value. But truth be told, hasClass() is just a convenient wrapper for the is() method*/

    // Alerts "1"
    //alert($('a[title="jQuery"][href^="http://"][class!=""]').length);
    
    // Get all checkboxes that are both visible and checked
$(':checkbox:visible:checked')

});