Conditionally include additional CSS and JS for page templates in WordPress

wp_conditional_enqueue_styles_and_scripts.php

<?php
if ( ! defined( 'WPINC' ) ) { die('Direct access prohibited!'); }
/**
 * Conditionally include additional CSS and JS for page templates
 */
function conditionally_enqueue_scripts()
{
    // Test for page template
    if( is_page_template() )
    {
        // Get template name and assign
        $name = rtrim( basename( get_page_template() ), '.php' );

        // Test for existence of CSS file with same name
        if( file_exists( get_template_directory() . '/css/' . $name . '.css' ) )
        {
            // Enqueue the CSS
            // For options, see: https://developer.wordpress.org/reference/functions/wp_enqueue_style/
            wp_enqueue_style( $name . '_css', get_template_directory_uri() . '/css/' . $name . '.css', false );
        }

        // Test for existence of JS file with same name
        if( file_exists( get_template_directory() . '/js/' . $name . '.js' ) )
        {
            // Enqueue the JS
            // For options, see: https://developer.wordpress.org/reference/functions/wp_enqueue_script/
            wp_enqueue_script( $name . '_js', get_template_directory_uri() . '/js/' . $name . '.js', array(), false, true );
        }
    }
}
add_action( 'wp_enqueue_scripts', 'conditionally_enqueue_scripts' );