Enqueuing jQuery in plug-ins

Question

I want to use jQuery in a plugin. In functions.php of the theme I'm using, I found:

if(!is_admin()) {
        wp_deregister_script('jquery');
        wp_register_script('jquery', 'http://ajax.googleapis.com/ajax/libs/jquery/1.5.0/jquery.min.js');

As I understand it, this loads jQuery and I'm ready to go. All I have to do is add this to my plugin's javascript file:

jQuery(document).ready(function($) {

    //put jquery code here

})

A) Is that it? Am I missing anything?

I did not see this in the header.php:

<?php wp_enqueue_script('jquery');?>
<?php wp_head(); ?>

B) I'd also like to use jquery-ui. In a plugin that came with the theme, I found:

wp_enqueue_script("jquery-ui-sortable");
wp_enqueue_script("jquery-ui-draggable");
wp_enqueue_script("jquery-ui-droppable"); 

Do I simply do the same as above in own plugin? And then call it in my js file as:

jQuery(document).ready(function($){

}

What if I want to use other bits of the jQuery-UI library? How can I tell which parts of jQuery-UI are included in the theme?

Sorry for the basic questions. I want to make sure that I'm set-up properly and I understand what's going on.

---

Additional Info:

Let's say I've got a plugin called "myplugin". The plugin works. But, I want to add some jQuery functionality. In myplugin's main function I add:

wp_enqueue_script('myplugin_script', 'http://mysite/wp-content/plugins/myplugin/js/myplugin_script.js');

In myplugin_script.js, I have:

jQuery.noConflict();

jQuery(document).ready(function($) {                
    alert("Hello");                                                                     
})

Why isn't the alert popping up? Do I need to add the script to a hook? Or will wp_enqueue_script cause it to fire?

Thank you.

-Laxmidi

Answer 1

First of all, if your code (or the theme's code) is unregistering jQuery and re-registering it from another location (Google), you need to add this somewhere:

jQuery.noConflict();

This makes jQuery cooperate with other scripts (i.e. Prototype) that try to define the $ variable globally. WordPress has this line bundled into their version, Google does not.

If you need to enqueue jQuery and a bunch of jQuery UI stuff, you'll need to do that.

function my_enqueue() {
    wp_enqueue_script('jquery');
    wp_enqueue_script("jquery-ui-sortable");
    wp_enqueue_script("jquery-ui-draggable");
    wp_enqueue_script("jquery-ui-droppable"); 
}
add_action( 'wp_enqueue_scripts', 'my_enqueue' );

This will hook your enqueues to the appropriate action that will output them in the header. I'm assuming that the jQuery UI scripts are already registered within WordPress.