Programmatically Add Font-Awesome Icons to Category Widget

I use the Categories widget on my sidebar(s) and I would like to display a Font Awesome icon next to each category listed in the widget. The icon would be the same for all categories, for now, but I would like to give each category it’s own unique icon in the future.

I would like to modify the Categories widget using code in my functions.php file to add the icon by inserting markup like <i class="fa fa-chevron-right"></i> into category’s link/anchor element after the category’s title. I could accomplish this via CSS, but in doing so I lose the ability to programmatically determine which icon to display, along with the flexibility for other improvements/changes that I may wish to make in the future.

Basically, I wish to achieve this effect:

Cat 1          >

Cat 2          >

Cat 3          >

_{(The greater-than symbol ‘>’ represents the icon placement relative to the category title)}

I have Font Awesome enqueued in the functions.php file using the wp_enqueue_scripts hook as follows, and it loads and displays the icons perfectly. Note that I do not use any Font Awesome plugin built for WordPress.

/* Enqueue Scripts
-----------------------------------------------------------------*/
add_action( 'wp_enqueue_scripts', 'essentials_enqueue_scripts' );
function essentials_enqueue_scripts() {
    /* jQuery */
    wp_enqueue_script('jquery');
    wp_enqueue_script( 'jquery_ui', "http" . ($_SERVER['SERVER_PORT'] == 443 ? "s" : "") . "://ajax.googleapis.com/ajax/libs/jqueryui/2.0.3/jquery-ui.min.js", false, null);
    wp_enqueue_script( 'waypoints', get_template_directory_uri() . '/js/waypoints.min.js');
    wp_enqueue_script( 'essentials_main', get_template_directory_uri() . '/js/essentials_main.js', array(), '1.0.0', true );
    wp_enqueue_script( 'essentials_show_stuff', get_template_directory_uri() . '/js/essentials_show_stuff.js', array(), '1.0.0', true );
    /* Google Fonts */
    wp_register_style('GoogleFonts','http://fonts.googleapis.com/css?family=Open+Sans:300,400,600,700,800|Bad+Script');
    wp_enqueue_style( 'GoogleFonts');
    /* Font Awesome Fonts */
    wp_register_style('Font Awesome','//netdna.bootstrapcdn.com/font-awesome/4.0.3/css/font-awesome.css');
    wp_enqueue_style( 'Font Awesome'); 
}

Despite my best research efforts, I was unable to find a solution to modify the categories widget.

Assumptions:

You don’t explain how you want to install the Font Awesome package, so I just assume for the moment that you use the plugin Font Awesome Icons.

You wrote:

Before anyone says use a background image, I do not want to do that. I
would like it to be physical.

so I assume you want to use the <i> tag directly, for example:

<i class="fa icon-caret-right"></i>

after each category link in the widget category list.

Idea:

You can use the wp_list_categories filter to modify the output of the widget category list.

Example:

Here is a simple example how to inject it into the category list via the wp_list_categories filter:

/**
 * Inject Font Awesome <i> tag after each widget category link
 *
 * @param string $output
 * @return string $output
 */

 function custom_wp_list_categories( $output )
 {  
     remove_filter( current_filter(), __FUNCTION__ ); 
     return str_ireplace( '</li>', '<i class="fa icon-caret-right"></i></li>', $output);
 }

 add_action( 'widgets_init', function(){
     add_filter( 'wp_list_categories', 'custom_wp_list_categories' );
 });

This will give you an output similar to this one: