defer-wp-scripts.php

defer-wp-scripts.php

<?php   
  /*
  function to add async and defer attributes
  Will only work if the scripts are enqueued with wp_enqueue_script()
  */
  function defer_js_async($tag){

    ## 1: list of scripts to defer.
    $scripts_to_defer = array(
      'owl-carousel.min.js',
      'mansonry.js',
      'imgloaded.js',
      'jquery.magnific-popup.min.js',
      'bgswitcher.js',
      'exit.js',
      'lazyload.js',
      'app.js',

      // WooCommerce
      'add-to-cart.min.js',
      'cart-fragments.min.js',
      'jquery.cookie.min.js',
      'jquery.blockUI.min.js',
      'woocommerce.min.js',

      // Wordpress

      'wp-embed.min.js'
    );


    #defer scripts
    foreach($scripts_to_defer as $defer_script){
      if(true == strpos($tag, $defer_script ) )
      return str_replace( ' src', ' defer="defer" src', $tag );
    }

    return $tag;
  }

  // You can wrap this hook is a wp_is_mobile() function if you want this behavior only on mobile
  add_filter( 'script_loader_tag', 'defer_js_async', 10 );