How to Properly Add JavaScripts and Styles in WordPress

Recently we did a code review for a plugin one of our users wrote. The plugin worked fine, but the developer wasn’t following the best practices on loading external JavaScript. WordPress has an enqueue system to add external scripts and styles which helps prevent plugin conflicts. Since most users run more than one plugin on their site, it is always good for developers to follow the best practice. In this article, we will show you how to properly add JavaScripts and styles in WordPress. This will be particularly useful for those who are just starting to learn WordPress theme and plugin development.

The Mistake

WordPress have a wp_head function that allows you to load anything in the head section of the site. For those who don’t know better, they simply add their scripts by using a code like this:

<?php

add_action('wp_head', 'wpb_bad_script');

function wpb_bad_script() {

echo 'jQuery goes here';

}

?>

While the above code is an easy way, it is the wrong way of adding scripts in WordPress. For example, if you load jQuery manually and another plugin that also uses jQuery loads it through the proper way, then you have jQuery being loaded twice. It is also possible that the two are different versions which can also cause conflicts.

Let’s look at the right way of doing this.

Why Enqueue Scripts in WordPress?

WordPress has a strong developer community. Thousands of people around the world design themes and write plugins for WordPress. To make sure that everything works properly and no one is stepping on another’s toe, WordPress has an enqueue script function. This function provides a systematic way of loading JavaScripts and styles. By using wp_enqueue_script function, you tell WordPress when to load a script, where to load it, and what are it’s dependencies.

This allows everyone to utilize the built-in JavaScript libraries that comes bundled with WordPress rather than loading the same third-party script multiple times. It also helps reduce page load time and avoid conflicts with other themes and plugins.

How to Properly Enqueue Scripts in WordPress

Loading the scripts properly in WordPress is very easy. Below is an example code that you would paste in your plugins file or in your theme’s functions.php file to properly load scripts in WordPress.

<?php

 function wpb_adding_scripts() {

wp_register_script('my_amazing_script', plugins_url('amazing_script.js', __FILE__), array('jquery'),'1.1', true);

wp_enqueue_script('my_amazing_script');

}

 add_action( 'wp_enqueue_scripts', 'wpb_adding_scripts' );  

?>

Explanation:

We started by registering our script through the wp_register_script() function. This function accepts 5 parameters:

§  $handle – Handle is the unique name of your script. Ours is called “my_amazing_script”

§  $src – src is the location of your script. We are using the plugins_url function to get the proper URL of our plugins folder. Once WordPress finds that, then it will look for our filename amazing_script.js in that folder.

§  $deps – deps is for dependency. Since our script uses jQuery, we have added jQuery in the dependency area. WordPress will automatically load jQuery if it is not being loaded already on the site.

§  $ver – This is the version number of our script. This parameter is not required.

§  $in_footer – We want to load our script in the footer, so we have set the value to be true. If you want to load the script in the header, then you would say false.

After providing all the parameters in wp_register_script, we can just call the script in wp_enqueue_script() which makes everything happen.

Now some might wonder why are we going the extra step to register the script first and then enqueuing it? Well, this allows others the site owner to deregister your script if they want to without modifying the core code of your plugin.

How to Properly Enqueue Styles

Just like scripts, you can also enqueue your stylesheets. Look at the example below:

<?php

function wpb_adding_styles() {

wp_register_script('my_stylesheet', plugins_url('my-stylesheet.css', __FILE__));

wp_enqueue_script('my_stylesheet');

}

add_action( 'wp_enqueue_scripts', 'wpb_adding_styles' ); 

?>

Notice that we have used wp_enqueue_scripts action hook for both styles and scripts. Despite the name, this function works for both.

In the examples above we have used plugins_url to point to the location of the script or style we wanted to enqueue. However, if you are using the enqueue scripts function in your theme, then simply use get_template_directory_uri() instead. If you are working with a child theme, then useget_stylesheet_directory_uri(). Below is an example code:

<?php

function wpb_adding_scripts() {

wp_register_script('my_amazing_script', get_template_directory_uri() . '/js/amazing_script.js', array('jquery'),'1.1', true);

wp_enqueue_script('my_amazing_script');

}

add_action( 'wp_enqueue_scripts', 'wpb_adding_scripts' ); 

?>

We hope this article helped you learn how to properly add JavaScripts and stylesheets in your WordPress themes and plugins. 

Additional Resources:

• wp_enqueue_script
• wp_register_script
• wp_enqueue_scripts