react usestate useeffect code example

Example 1: useeffect

function App() {
  const [count, setCount] = useState(0);

  useEffect(() => {
    longResolve().then(() => {
      alert(count);
    });
  }, []);

  return (
    <div>
      <button
        onClick={() => {
          setCount(count + 1);
        }}
      >
        Count: {count}
      </button>
    </div>
  );
}

Example 2: useeffect react

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

Example 3: useeffect react

useEffect(() => {
  window.addEventListener('mousemove', () => {});

  // returned function will be called on component unmount 
  return () => {
    window.removeEventListener('mousemove', () => {})
  }
}, [])

Example 4: react hook usestate

function Counter({initialCount}) {
  const [count, setCount] = useState(initialCount);
  return (
    <>
      Count: {count}
      <button onClick={() => setCount(initialCount)}>Reset</button>
      <button onClick={() => setCount(prevCount => prevCount - 1)}>-</button>
      <button onClick={() => setCount(prevCount => prevCount + 1)}>+</button>
    </>
  );
}

Example 5: 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 6: react useeffect

import React, { useState, useEffect } from 'react';
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>
  );
}