Async / Defer JS

"Async Defer JS" is a module which adds a configuration that says what HTML scripts should get an "async" or "defer" attribute.

It acts upon scripts added as page assets. A script which is added by a third party through some other way than a page asset won't get the "async" or "defer" attribute even if it matches one of the regular expressions configured.

Installation

Run the following command in the root of Magento 2.

$ composer require weprovide/magento2-module-async-defer-js

Once installed the only thing left to do is actually enable it.

$ bin/magento module:enable WeProvide_AsyncDeferJs
$ bin/magento setup:upgrade --keep-generated

Configuration

In System > Configuration > Advanced > Developer > JavaScript Settings two configuration settings can be seen. One of them is the regular expression used for the async HTML attribute, the other for defer.