README

Lazy loader for WordPress theme.

Installation

Use composer.

composer require kunoichi/assets-lazy-loader

Usage

Enable each services 1 by 1 in your functions.php.

// in your functions.php
require __DIR__ . '/vendor/autoload.php';

ImageLazyLoader

Filter all img tag in your HTML and add loading="lazy" attributes. If the img tag already has loading attribute, no more attribute will be added.

// Enable image lazy loader.
Kunoichi\AssetsLazyLoader\ImageLazyLoader::enable();
// If you want exclude some image(e.g. Featured image)
// a filter hook is available.
add_filter( 'assets_lazy_loader_image', function( $should, $tag ) {
	return false !== strpos( $tag,  'size-post-thumbnail' );
}, 10, 2 );

Deferred Scripts

Add defer attributes to JavaScripts enqueued with wp_enqueue_script.

Kunoichi\AssetsLazyLoader\ScriptsDefer::enable( [
	'exclude'  => ['jquery-core'], // Only jQuery is not deferred.
	'in_login' => true, // Add defer on login screen. Default false.
	'in_admin' => true, // Same as above.
] );

Some JavaScripts have following scripts via wp_add_inline_script. This may cause critical erros. ScriptDefer skips enqueued scripts with after section, but for more safety, consider allow list approach.

Kunoichi\AssetsLazyLoader\ScriptsDefer::enable( [
	// Defer scripts only which you know they are safe with defer attribute.
	'exclude'  => [ 'your-js', 'jquery' ], 
] );

CSS Preload

Add rel="preload" to link tag and fallback scripts.

Kunoichi\AssetsLazyLoader\StyleLoader::enable( [
	'exclude'  => StyleLoader::admin_critical( ['twentytwenty-style'] ), // Exclude default style and login/admin screen.
	'in_login' => true,
	'in_admin' => true,
] )

CSS preload caused non styled html in few seconds. To avoid shrinking of the screen by re-rendering, exclude critical css files from preload. In many case, it's the theme's main styelsheed.

StyleLoader::admin_critical is helpful for excluding ciritcal css in admin and login screen.

jQuery Enhancement

The default jQuery bundled with WordPress has some issued.

• Version is old(1.12.4).
• Shipped with jQuery migrate unnecessory for sane plugins and themes.
• Enqueued in head tag.

You can assign other version of jQuery and drop jquery-migrate.

JqueryOptimizer::enable( [
	'footer'  => true, // Move jQuery to footer.
	'src'     => 'https://code.jquery.com/jquery-3.5.1.slim.js', // Slim version from https://code.jquery.com/
	'version' => '3.5.1', // Specify collect version.
] );

Ackowledgements

• CSS preload depends on fg-loadcss v2.1.0 by Filament Group.

License

GPL 3.0 or later.