is_page_template & is_page in functions.php not working

Question

I use the following script to call the maps JavaScript in the page-about.php template. But its actually not working. The scripts are executed nowhere:

// Load maps scripts
function maps_scripts()
{   
    // If query if current Page is not wp-login-php or admin page
    if ( is_page_template('page-about.php') ) {
        wp_register_script('gmapsapi', 'http://maps.google.com/maps/api/js?sensor=false', array(), '1.0.0', true); 
        wp_enqueue_script('gmapsapi');

        wp_register_script('gmaps', get_template_directory_uri() . '/js/gmaps.min.js', array(), '1.0.0', true); 
        wp_enqueue_script('gmaps'); 

        wp_register_script('map', get_template_directory_uri() . '/js/map.js', array(), '1.0.0', true); 
        wp_enqueue_script('map'); 
    } 
}

add_action('init', 'maps_scripts');

I also tried with is_page() but its not working. When I delete the if statements the scripts are loaded on all pages.

Answer 1

Use wp_enqueue_scripts instead on init. This will ensure you the template is already loaded.

add_action('wp_enqueue_scripts', 'maps_scripts');

Or you try to check the template using get_page_template_slug() instead of is_page_template:

$tmp = get_page_template_slug($post_id); // provide page/post ID
if('page-about.php' == $tmp) {
    // enqueue scripts here
}

Note that you don't need to register scripts before enqueueing them. Simply pass all the parameters of wp_register_script directly to the wp_enqueue_script (see the Code Reference).