Check if jquery library exist

How to check if jQuery library exist in head tags?

<head>
<script type="javascript/text" src="http://code.jquery.com/jquery-1.6.2.js"></script>
</head>

and if not exist how do I load in head tags the jquery library, I’m doing a plugins and I want to load my plugins script in jQuery and also do able to check if jQuery library exist so my jQuery script will run

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4 comments

  1. scripts and styles should never be embedded directly in themes or templates because of potential conflicts between plugins and themes.

    To use jQuery in a plugin or theme it should be enqueued with wp enqueue script. This will make sure it’s added only once, and any scripts that define it as a dependency will load after.

  2. You can check whether the jQuery library already exist/loaded in the site and load it if not using the following code.

    function load_jquery() {
        if ( ! wp_script_is( 'jquery', 'enqueued' )) {
    
            //Enqueue
            wp_enqueue_script( 'jquery' );
    
        }
    }
    add_action( 'wp_enqueue_scripts', 'load_jquery' );
    
  3. @Milo already pointed this out, just enqueue your script with jQuery listed as a dependency. When WordPress loads your script, it will see the dependency and load jQuery for you automatically. For example:

    function enqueue_my_scripts(){
        if( ! is_admin() )
            wp_enqueue_script( 'stacked-script', get_bloginfo('stylesheet_directory') . '/scripts/stacked.js', array('jquery'), '1.0.1' );
    }
    add_action( 'wp_enqueue_scripts', 'enqueue_my_scripts' );
    

    Will put the following in the header of your site:

    <script type='text/javascript' src='http://site-url.com/wp-includes/js/jquery/jquery.js?ver=1.6.1'></script> 
    <script type='text/javascript' src='http://site-url.com/wp-content/themes/stacked-theme/scripts/stacked.js?ver=1.0.1'></script> 
    

    jQuery will be loaded first, followed by your script.