WP Deferred JavaScripts

WP Deferred JavaScripts


This plugin defer the loading of all JavaScripts added by the way of wp_enqueue_script(), using LABJS. The result is a significant optimization of loading time.

It is compatible with all WordPress JavaScript functions (wp_localize_script(), js in header, in footer…) and works with all well coded plugins.

If a plugin or a theme is not properly enqueuing scripts, your site may not work. Check this page: Function Reference/wp_enqueue_script on WordPress Codex.

LABjs (Loading And Blocking JavaScript) is an open-source (MIT license) project supported by Getify Solutions.

We performed a range of tests to determine the potential benefit of loading time. On wabeo we executed webwait (150 calls by test). Result is this plugin could improve your loading time by 25%!!
More information in the Screenshots section.

You can find more information about WP Deferred JavaScripts and technical information about asynchronous scripts on authors blogs.


WP Deferred JavaScript includes some hooks. If you never used one of them, check this page. It’s better to use those filters in a plugin or a mu-plugin.

Exclude Scripts

do_not_defer is a filter that took as a parameter an array containing scripts that should be handle normally.

Here is an example:

// Normal script enqueue. add_action( 'wp_enqueue_scripts', 'register_canvas_script' ); function register_canvas_script() {     wp_register_script( 'my-canvas-script', 'http://exemple.com/myscript.js' );     wp_enqueue_script( 'my-canvas-script' ); }  // Don't defer this script. add_filter( 'do_not_defer', 'exclude_canvas_script' ); function exclude_canvas_script( $do_not_defer ) {     $do_not_defer[] = 'my-canvas-script';     return $do_not_defer; } 

Since 2.0.3 you can also use the WP Deferred JS settings pannel!


wdjs_labjs_src is a filter that allow you to change LabJS URL.
($lab_src, $lab_ver)

// for example, I need a specific version of LabJS add_filter( 'wdjs_labjs_src', 'my_labjs_src', 10, 2 ); function my_labjs_src( $src, $ver ) {     if ( '2.0' !== $ver ) {         // Hotlinking raw github is a bad practice, I did it just for the lulz.         return 'https://raw.githubusercontent.com/getify/LABjs/edb9fed40dc224bc03c338be938cb586ef397fa6/LAB.min.js';     }     return $src; } 
HTML5 compatibility

If you use HTM5, wdjs_use_html5 is a filter that remove the type="text/javascript" attribute. You can use it this way:

add_filter( 'wdjs_use_html5', '__return_true' ); 
Change a script URL

wdjs_deferred_script_src can be used to change the way one of the script is loaded. For example:

// Here, I need to add information about the charset. add_filter( 'wdjs_deferred_script_src', '', 10, 3 ); function change_my_script_src( $src_string, $handle, $src ) {     // $src_string -> .script("http://exemple.com/myscript.js?v=2.0")     // $handle -> my-script     // $src -> http://exemple.com/myscript.js?v=2.0     $out = array( 'src' => $src, 'charset' => 'iso-8859-1' );     return '.wait(' . json_encode( $out ) . ')'; } 
How to execute a code right after script loading

You may need to execute a script right after its loading. You can use wdjs_deferred_script_wait filter to do it.

add_action( 'wdjs_deferred_script_wait', 'after_my_script', 10, 2 ); function after_my_script( $wait, $handle ) {     if ( 'my-script' === $handle ) {         $wait = 'function(){new MyScriptObject();}';     }     return $wait; } 
Execute a function when all scripts are loaded

You may have to use inline JavaScript in your footer. If that’s the case, you will have to use that last hook to make it compatible with WP Deferred JavaScripts.

You will have to wrap this inline JS into a new function. Then, you will have to use wdjs_before_end_lab to execute it.

// This is a fake function that we are wrapping in a new function add_filter( 'before_shitty_plugin_print_js', 'wrap_this_code' ); function wrap_this_code( $code ) {     return 'function PluginShittyCode(){' . $code . '}'; }  add_filter( 'wdjs_before_end_lab', 'call_shitty_code' ); function call_shitty_code( $end ) {     $end .= '.PluginShittyCode()';     return $end; } 

WP Deferred JavaScripts