[WordPress][Simple Map] Load Google Maps API script from Simple Map deferred.

simple-map-defer.php

<?php
defined( 'ABSPATH' ) or die( 'No direct access here.' );
/**
 * Plugin Name: Simple Map | Defer
 * Description: Makes sure Google Maps API script from <a href="https://wordpress.org/plugins/simple-map/">Simple Map</a> gets loaded deferred.
 * Author:      Caspar Hübinger
 * Author URI:  https://profiles.wordpress.org/glueckpress
 * Plugin URI:  https://gist.github.com/glueckpress/56c88900aad391b95b5d44f4e752a1a4
 * License:     GNU General Public License v3 or later
 * License URI: http://www.gnu.org/licenses/gpl-3.0.html
 */

/**
 * Make defer.
 * @link https://matthewhorne.me/defer-async-wordpress-scripts/
 */
add_filter( 'script_loader_tag', function ( $tag, $handle ) {

	// Defer
	$defer_scripts = array( 'simplemap', 'google-maps-api' );

	foreach( $defer_scripts as $defer_script ) {

		if ( $defer_script === $handle ) {
			return str_replace( ' src', ' defer="defer" src', $tag );
		}
	}

	return $tag;

}, 10, 2 );