What is React useEffect?

About

useEffect is an effect that:

• is asynchronous
• and executes at the end of the rendering.

Specifically, it runs at the end of a commit after the screen updates, after every render

• When you want to do something with the DOM node (outside rendering)
• The DOM element does not exist yet (not yet rendered)
• To synchronize with an external system (editor)

In React, rendering should be a pure calculation of JSX and should not contain side effects like modifying the DOM.

Don't useState as it will trigger a new render, that will trigger useEffect again

You can tell React:

• to skip unnecessarily re-running the Effect by specifying an array of dependencies as the second argument,
• even an empty array to run once.

Support

Warning: Cannot update a component () while rendering a different component ().

Typically, if you get this message, you need to encapsulate your state in a useEffect function

Warning: Cannot update a component (`xxxxx`) while rendering a different component (`xxxxxx`). 
To locate the bad setState() call inside `xxxx`, follow the stack trace as described in https://reactjs.org/link/setstate-in-render