react when to use useeffect code example

Example 1: useeffect react

useEffect(() => {
	//  code goes here
    return () => {
      // cleanup code codes here
    };
  },[]);

Example 2: react useeffect

import React, { useEffect } from 'react';
	
	const [data,setData]=useState()
    useEffect(() => {
        fetch(`put your url/api request in here`)
        .then(res=>res.json())
        .then(json => setData(json))
    },[])

Example 3: react hook useeffect

//This is a basic example, carefully read the docs as
//useEffect it's like componentDidMount/WillUnmount
function Example() {
  const [count, setCount] = useState(0);

  // Similar to componentDidMount and componentDidUpdate:
  useEffect(() => {
    // Update the document title using the browser API
    document.title = `You clicked ${count} times`;
  });
  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={() => setCount(count + 1)}>
        Click me
      </button>
    </div>
  );
}