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WP Deferred JavaScripts

By Willy Bahuaud

Performance & Optimization / Caching Solutions

Reviewed by Omar Dabbas

Trusted WordPress expert with 20+ years of experience evaluating plugins for the WP ecosystem.

WP Deferred JavaScripts Review - In-Depth Analysis

Defer loading of JavaScripts added with wp_enqueue_script for better performance. Uses LABJS for asynchronous loading.

Performance Overview

WPS Score

6.61/10

User Rating

3.2/5 (based on 35+ reviews)

Active Installations

800+

Update Frequency

Below Average It is calculated using the weighted average of same category plugins.

Security Score

1 / 10 (Very Low Risk) It is calculated using the weighted average of all versions.

What It Does

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 and works with all well coded plugins.

If a plugin or a theme is not properly enqueuing scripts, your site may not work. Check the WordPress Codex for more information.

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

We performed a range of tests to determine the potential benefit of loading time. This plugin could improve your loading time by 25%.

More information can be found in the Screenshots section.

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

Comparing to Alternatives

WP Deferred JavaScripts is one of several plugins designed to optimize JavaScript loading on WordPress sites. It faces competition from multiple alternatives that offer similar or enhanced features.

Top alternatives

Strengths

Effectively defers JavaScript to improve page load speed.
Works well with PHP7 and latest WordPress versions as tested.
Simple to use for fine-tuning JavaScript loading.
Unique in actively deferring JS compared to some alternatives.
Free to use without a paid version.

Weaknesses

Can cause conflicts with caching plugins leading to site breakage.
Lacks clear options to exclude specific scripts from deferring.
Compatibility issues with popular plugins like Contact Form 7 and Visual Composer.
Limited support and documentation for troubleshooting conflicts.

User Sentiment Analysis

User reviews are mixed with nearly half of the ratings being 1 or 2 stars, indicating significant issues for some users, while others report effective performance and ease of use.

Positive highlights

"Works Perfectly – Negative Reviews are due to Plugin Conflicts" – tigershroof
"Great! Use if you need to fine tune speed of your website" – capbussat
"It is the only plugin that actively defers JS effectively." – tigershroof

Common complaints

Breaks Google Maps functionality on sites.
Causes issues with Ajax in Contact Form 7.
Stops dropdown menus from working in some themes like Avada.
Conflicts with Visual Composer causing navigation menu problems.
Lack of support and guidance on excluding scripts from deferring.

Weaknesses

Plugin can break essential site features due to aggressive deferring.
No clear user controls to manage script exclusions.
Support is unresponsive or unhelpful according to users.
May require technical knowledge to troubleshoot conflicts.

Who Should Use This?

Best for

Users looking for a free, straightforward plugin to defer JavaScript and improve site speed, who are comfortable troubleshooting potential conflicts and fine-tuning settings.

Not ideal for

Sites relying heavily on plugins like Google Maps, Contact Form 7, or Visual Composer without technical support, or users seeking a plugin with robust support and easy script exclusion options.

Pricing & Value

Free version includes

The free version includes the core functionality to defer JavaScript files to improve page load times without any paid upgrade options.

Final Verdict

WP Deferred JavaScripts offers a free and effective solution for deferring JavaScript to enhance website speed, with positive feedback from users who successfully fine-tune their setups. However, it has notable compatibility issues with popular plugins and lacks user-friendly options to exclude scripts, which can cause site functionality problems.

While it stands out for its active deferring capability, the plugin's limited support and potential for conflicts mean it is best suited for users comfortable with technical troubleshooting. Alternatives with more features or better compatibility may be preferable for less technical users.

Other Notable Features

Here are a few other notable features of this free WP Deferred JavaScripts plugin.

Deferring

Javascript

Labjs

Optimization

Performance

Screenshots

FAQ

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; }

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' );

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 ) . ')'; }

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; }

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; }