import React, { useState, useEffect, useRef, useContext, useReducer, useMemo } from 'react'; export default () => { const [count, setCount] = useState(0); useLayoutEffect(() => console.log("each render 1")); console.log("each render 2"); useEffect(() => { console.log("each render 3"); return () => { console.log(4); }; }, [count]); return ( <button onClick={() => setCount((prevProps) => ++prevProps)}> Increment </button> ); }

In this React component, the following occurs:

1. useLayoutEffect(() => console.log("each render 1"));

   • Called after all DOM mutations, synchronously before the browser repaints.
   • Executes after every render.

2. console.log("each render 2");

   • Executes on every render of the component, within the function body.

3. useEffect(() => { ... }, [count]);

   • Executes after every change of count.
   • On each change of count, the cleanup function (which logs 4) is called first, then the main effect (logs "each render 3").

4. The button increments count by 1 on click.

Order of logs on the first render:

• "each render 2" (inside the component)
• "each render 1" (useLayoutEffect)
• "each render 3" (useEffect)

When count changes:

• "each render 2"
• "each render 1"
• "4" (cleanup of the previous effect)
• "each render 3"

Note that useLayoutEffect is called synchronously after rendering, while useEffect is called asynchronously after painting.

Also, it is recommended to fix the increment in setCount: better to use prev => prev + 1 instead of ++prev to avoid side effects:

<button onClick={() => setCount(prev => prev + 1)}>
  Increment
</button>