Easy theme overrides for when updates a site with a build process.

theme_overrides.php

<?php
/**
 * Easy theme overrides for when updating a site with a build process in WordPress
 * @author Dean Oakley
 * http://thriveweb.com.au
 * Add overrides.css and overrides.js to your theme directory and edit away
 */ 
 
add_action("wp_enqueue_scripts", "theme_overrides", 20);
function theme_overrides() {

  wp_enqueue_script(
    'js_overrides',
    get_template_directory_uri().'/overrides.js',
    null,
    filemtime( get_stylesheet_directory().'/overrides.js' ),
    true
  );

  wp_enqueue_style(
    'css_overrides',
    get_stylesheet_directory_uri().'/overrides.css',
    array(),
    filemtime( get_stylesheet_directory().'/overrides.css' )
  );
 
 }