Javascript Async and Defer

Introduction

If async is not present and defer is present: The script is executed when the page has finished parsingIf async is present: The script is executed asynchronously with the rest of the page (the script will be executed while the page continues the parsing)

Improve your page loading time by allowing javascript loading asynchronously
You will see the difference with YSlow and Google Page speed ranking but your visitors will thank you for providing a speedy website.

When a browser loads a webpage, it will start by loading external Javascript and CSS ressources before loading the html and render it's content.

If neither async or defer is present: The script is fetched and executed immediately, before the browser continues parsing the page

This will improve your global page loading time

However, this is not applicable to all scripts as you want to make sure the script is loaded while some other script or inline script will call it.

Usually, if your jQuery inline scripts are called within a jQuery(document).ready() declaration, you can safely load the javascript file asynchronously.

Write a review

Does a good job!

Hekate (26).
Posted on 10 September 2023

Functionality

Excellent! A very practical, much-needed extension that works out of the box. No problems. Improves loading times in a fast, easy way.

Ease of use

Just add your scripts, chose defer or async (or both) and that's it.

Support

Documentation

Not needed. It is pretty much self-explanatory and simple to use.

I used this to: Improving loading times. I tested the results in several pages and the improvement was significant.

Increíble!!!

Luz Quintero (5).
Posted on 05 February 2020

Functionality

Funciona tal como dice la documentación. Llevaba tiempo tratando de mejorar la velocidad de mis webs y nada funcionaba, ha mejorado 100%

Ease of use

Conocimientos básicos. Sólo instalar y la extensión hace el resto. Si se necesitan acciones avanzadas la documentación ayuda a hacerlo.

Support

No he necesitado ayuda, pero los links de contacto son fáciles de reconocer

Documentation

Está al alcance del usuario. Sin embargo no he necesitado usarla.

I used this to: Para aumentar la velocidad de mi web y corregir conflictos de javascript

Yes, it works!

userakos (5).
Posted on 28 February 2018

Functionality

I came happily here to say that the improvement in Google PageSpeed Insights was significant! Now my score is fully green.

Ease of use

Can't be simpler.

Support

Not needed.

Documentation

Not needed.

I used this to: Make my websites have a better score in Google PageSpeed Insights, GTMetrix etc.

Perfect

Plamen (7).
Posted on 06 November 2016

Functionality

As described. Improved speed.

Ease of use

Only few controls.
Files should be added manually.
Care needed regarding proper usage of file paths.
Consider automated process next version

Support

Not needed. Email and contact form provided. Forum n/a.

Documentation

Short and precise. See home page.

I used this to: Small site with news and lot of pictures.

Good

Ian Leahy (4).
Posted on 05 July 2016

Functionality

Good

Ease of use

It took me awhile to get the paths down of the files. So here is how you have to put them in:
/media/jui/js/bootstrap.min.js

Support

Documentation

Works as described

Terry Carter (3).
Posted on 26 January 2016

Functionality

This plugin works exactly as described. PageSpeed and !YSlow score immediately went to 100% rating after activating and configuring.

Ease of use

Simple to use, activate plugin and add the links to the scripts being loaded by your site.

Support

Support was not needed even though the documentation is self explanatory.

Documentation

Documentation should probably tell the lesser advanced users where they can look in HTML source to view scripts being loaded by Joomla.

I used this to: Deferring and Asynchronously loading scripts on my site.

Help on how to configure

djimman (1).
Posted on 12 October 2015

Functionality

Hello, i downloaded and installed plugin pretty easy, fast and accessible

Ease of use

Its easy to use, but i need some help on how to manually configure it, i mean i enable the 2 options but still i dont know which scripts add

Support

Documentation

I hope you make a tutorial on how to use it for the non experts

I used this to: defer parsing java

Great extension with superb support!

Ove Heradstveit (12).
Posted on 31 August 2015

Functionality

Works as expected!

Ease of use

Easy to setup, just needed to specify paths to javascripts that should be "asynced."

Support

The developer were very helpful when I had an issue with making the plugin work, and the problem got easily resolved based on his advice.

Documentation

Ok, could me some more information on troubleshooting.

I used this to: Making a bunch of javascripts load asynchronously, hereby enhancing the speed of my site.

It simply works

chris hoefliger (14).
Posted on 15 August 2015

Functionality

The plugin is not activated when installed, you have to do that manually, but that does not matter, as it wants to be configured anyway

Ease of use

It's simple and straightforward, not a big deal when it comes to make it work.
Full mark, says I.

Documentation

Is kept to a minimum - you've got to realise that you have to enter paths to you JS files without th single quotes around them.

I used this to: Used for several J!3.x sites to get better GTmetrix (and possibly Google) results. Especially when you have a load of JScript, it boosts 'Defer parsing of JavaScript' in Page Speed to near 100%

Thank you

Thank you (2).
Posted on 20 June 2015

Functionality

Works well - google improved

Ease of use

Very Easy

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