Force merged scripts created by “Merge + Minify + Refresh” to load asynchronously to improve site performance

merge-minify-refresh-async.php

<?php
/*
 * Plugin Name: Merge + Minify + Refresh: Force Async Scripts
 * Plugin URL: https://gist.github.com/macbookandrew/0bb0c29b2321c166845cea0b7cdb5d15
 * Description: Forces merged scripts created by “Merge + Minify + Refresh” to load asynchronously to improve site performance
 * Version: 1.0.0
 * Author: AndrewRMinion Design
 * Author URI: https://andrewrminion.com
 */

if (!defined('ABSPATH')) {
    exit;
}

/**
 * Add async attribute if the path contains MMR’s cache directory
 * @param  string $tag    HTML <script> tag
 * @param  string $handle WordPress’ internal handle for this script
 * @return string HTML <script> tag
 */
function mmr_add_async( $tag, $handle ) {
    if ( strpos( $tag, WP_CONTENT_URL . '/mmr' ) !== false ) {
        $tag = str_replace( ' src', ' async="async" src', $tag );
    }
    return $tag;
}
add_filter( 'script_loader_tag', 'mmr_add_async', 99, 2 );

Changelog

• 1.0.0: initial version