lightening aura - document.ready, window.onload alternative

The afterRender() function enables you to interact with the DOM tree after the framework’s rendering service has inserted DOM elements. It's not necessarily the final call in the rendering lifecycle; it's simply called after render() and it doesn't return a value. You generally want to extend default after rendering by calling superAfterRender() function before you add your custom code. 

Create ReRender component available in right side panel.

This code outlines a custom afterRender() function.

This is how it looks like: