UseEffect react

Useeffect umnount

  useEffect(() => {
    return () => {
      console.log("cleaned up");
    };
  }, []);

Useeffect react

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

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

Source: stackoverflow.com

UseEffect react

function FriendStatusWithCounter(props) {
  const [count, setCount] = useState(0);
  useEffect(() => {    document.title = `You clicked ${count} times`;
  });

  const [isOnline, setIsOnline] = useState(null);
  useEffect(() => {    function handleStatusChange(status) {
      setIsOnline(status.isOnline);
    }

    ChatAPI.subscribeToFriendStatus(props.friend.id, handleStatusChange);
    return () => {
      ChatAPI.unsubscribeFromFriendStatus(props.friend.id, handleStatusChange);
    };
  });
  // ...
}

Source: reactjs.org

Useeffect react

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

Useeffect react

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>
  );
}
Source:reactjs.org
3
React useEffect, useState

Useeffect react

useEffect(() => {
    // do something
  }, []);

-2

Similar codes

15 votes283 views2 answers
React native location
Javascript React
0 vote296 views1 answer
React document documentMode not found
Javascript React
3 votes297 views1 answer
White screen issue in react native splashscreen
Javascript React
0 vote308 views1 answer
React ES6 Arrow Functions
Javascript React
1 vote312 views1 answer
React form reload page
Javascript React
0 vote311 views1 answer
Number format reactjs
Javascript React
0 vote283 views1 answer
React break out of useeffect
Javascript React
0 vote329 views2 answers
Reactjs firebase timestamp to date
Javascript React
64 votes333 views7 answers
React router
Javascript React
1 vote364 views1 answer
How to add two elements in one path in react router v6
Javascript React