WordPress CSS & JS enqueue router

assets.php

<?php

/**
 * Routes specific js & css files to enqueue if they exist.
 *
 * (The idea is to use default.css & default.js for all your global styles,
 * then simply include default.css & default.js into your $template.css & template.js files
 * so that you can easily keep filesizes small and minimize the number of resources requested.)
 */
add_action( 'wp_enqueue_scripts', function() {
    $template = get_current_template(false, false);
    $css = file_exists( get_asset_file_path( "$template.js" ) ) ? "$template.css" : 'default.css';
    $js = file_exists( get_asset_file_path( "$template.js" ) ) ? "$template.js" : 'default.js';

    wp_enqueue_style(
        sanitize_title($css),
        get_asset_path($css),
        false,
        filemtime( get_asset_file_path( $css ) )
    );

    wp_enqueue_script(
        sanitize_title($js),
        get_asset_path($js),
        ['jquery'],
        filemtime( get_asset_file_path( $js ) ),
        true
    );
});

filters.php

<?php

/**
 * Define current template file
 *
 * Create global variables with the name of the current
 * theme template file being used.
 *
 * @param $template The full path to the current template
 */
add_filter( 'template_include', function ( $t ){
    $GLOBALS['current_theme_template'] = basename($t);
    $GLOBALS['current_theme_template_identifier'] = basename($t, '.php');
    return $GLOBALS;
}, 1000 );

helpers.php

<?php

/**
 * Get Current Theme Template Filename
 *
 * Get's the name of the current theme template file being used
 *
 * @global $current_theme_template Defined using define_current_template()
 * @param $echo Defines whether to return or print the template filename
 * @param $id Determines whether or not to include the file suffix
 * @return The name of the template filename, including .php
 */
function get_current_template( $echo = false, $with_suffix = true ) {
    $id = $with_suffix ? 'current_theme_template' : 'current_theme_template_identifier';
  
    if( !isset( $GLOBALS[$id] ) ) return false;
    
    if( $echo ) echo $GLOBALS[$id];

    return $GLOBALS[$id];
}

/**
 * gets the path to assets
 *
 * @return string
 */
function get_asset_path($path = null) {
    return get_stylesheet_directory_uri() . "/assets/{$path}";
}

/**
 * gets the file path to the asset
 *
 * @return string
 */
function get_asset_file_path($path = null) {
    return get_stylesheet_directory() . "/assets/{$path}";
}