react useeffect syntax

react useEffect

// Every rerender
useEffect(() => {
	console.log("I run everytime this component rerenders")
});

// onMount
useEffect(() => {
	console.log("I Only run once (When the component gets mounted)")
}, []);

// Condition based 
useEffect(() => {
	console.log("I run everytime my condition is changed")
}, [condition]);

// Condition based with "clean up"
useEffect(() => {
	console.log("I run everytime my condition is changed")
	
	return () => {
    	console.log("Use this return as a 'clean up tool' (this runs before the actual code)")
    }
}, [condition]);

Posted by: Guest on October-07-2021

function App() { const [count, setCount] = useState(0); useEffect(() => { longResolve().then(() => { alert(count); }); }, []); return ( <div> <button onClick={() => { setCount(count + 1); }} > Count: {count} </button> </div> ); }

import React, { useState } from 'react'; function Example() { // Declare a new state variable, which we'll call "count" const [count, setCount] = useState(0); return ( <div> <p>You clicked {count} times</p> <button onClick={() => setCount(count + 1)}> Click me </button> </div> ); }

useEffect is a hook for encapsulating code that has 'side effects,' and is like a combination of componentDidMount , componentDidUpdate , and componentWillUnmount . Previously, functional components didn't have access to the component life cycle, but with useEffect you can tap into it.23.1.2019

import React, { useEffect } from 'react'; export const App: React.FC = () => { useEffect(() => { }, [/*Here can enter some value to call again the content inside useEffect*/]) return ( <div>Use Effect!</div> ); }

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

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