DeferJs
This module uses the deferjs library to delay the loading of JavaScript files until the DOM is fully loaded, which can help improve your site's performance. It also offers options for custom delays and lazy loading of CSS and JavaScript.
DeferJs module is based on a tiny library deferjs.
Using this library we can delay or lazy load static resources like js and css.
This library also provide functionality of defering js files. It means, js files will not be loaded or excuted until entire DOM is loaded and rendered.
This module is very useful to fix Total Blocking Time.
In this module we have automated funtionality to defer, js files only, for other functionailties like custom delay css and js, lazyloading etc please refer to available option from library page deferjs
Configration
after installation, go to admin/config/performance/deferjs
keep the setting as per you use.