WooCommerce or any other plugin: Deliver JS and CSS through CDN without using a Plugin

WC()->plugin_url() is basically a wrapper for the core function plugins_url(). That functions return value is filtered. return apply_filters( 'plugins_url', $url, $path, $plugin ); So you should be able to add a filter to that hook that returns the initial value if $plugin isn’t woocommerce, then checks if the path or URL leads to one of the scripts you’re trying to replace and sends the appropriate value on from there.