FAQ: The Effect Hook - Separate Hooks for Separate Effects

This community-built FAQ covers the “Separate Hooks for Separate Effects” exercise from the lesson “The Effect Hook”.

Paths and Courses
This exercise can be found in the following Codecademy content:

Learn React

FAQs on the exercise Separate Hooks for Separate Effects

There are currently no frequently asked questions associated with this exercise – that’s where you come in! You can contribute to this section by offering your own questions, answers, or clarifications on this exercise. Ask or answer a question by clicking reply (reply) below.

If you’ve had an “aha” moment about the concepts, formatting, syntax, or anything else with this exercise, consider sharing those insights! Teaching others and answering their questions is one of the best ways to learn and stay sharp.

Join the Discussion. Help a fellow learner on their journey.

Ask or answer a question about this exercise by clicking reply (reply) below!
You can also find further discussion and get answers to your questions over in #get-help.

Agree with a comment or answer? Like (like) to up-vote the contribution!

Need broader help or resources? Head to #get-help and #community:tips-and-resources. If you are wanting feedback or inspiration for a project, check out #project.

Looking for motivation to keep learning? Join our wider discussions in #community

Learn more about how to use this guide.

Found a bug? Report it online, or post in #community:Codecademy-Bug-Reporting

Have a question about your account or billing? Reach out to our customer support team!

None of the above? Find out where to ask other questions here!

Note:
I have reported a bug. My code below was “passed” as valid from the existing “tests” installed in the dependency files. My code below is WRONG. The app did not work even though my code passed all the tests. So, I did find the errors by comparing my code to the solution and suggest if your app is not working you might compare your answer side by side to the solution to discover the simple fix. You can see in my code below the incorrect syntax was used for the setters.

setMenu(menuResponse.data);
setNewsFeed(newsFeedResponse.data);
setFriends(friendsResponse.data);

should have been

setMenu(response.data);
setNewsFeed(response.data);
setFriends(response.data);
//mine is different than the given solution but the Codecademy solution checker doesn't catch the mistakes. 
//you must compare to the solution to see your mistakes from this point.  
import React, { useState, useEffect } from 'react';
import { get } from './mockBackend/fetch';

export default function SocialNetwork() {
  const [menu, setMenu] = useState(null);
    useEffect(() => {
      get('/menu').then((response) => {
        setMenu(menuResponse.data);
      });
   }, []);

  const [newsFeed, setNewsFeed] = useState(null);
  useEffect(() => {
    get('/news-feed').then((reponse) => {
      setNewsFeed(newsFeedResponse.data);
    });
  }, []);

  const [friends, setFriends] = useState(null);
  useEffect(() => {
    get('/friends').then((response) => {
      setFriends(friendsResponse.data);
    });
   }, []);

  return (
    <div className='App'>
      <h1>My Network</h1>
      {!menu ? <p>Loading..</p> : (
        <nav>
          {menu.map((menuItem) => (
            <button key={menuItem}>{menuItem}</button>
          ))}
        </nav>
      )}
      <div className='content'>
        {!newsFeed ? <p>Loading..</p> : (
          <section>
            {newsFeed.map(({ id, title, message, imgSrc }) => (
              <article key={id}>
                <h3>{title}</h3>
                <p>{message}</p>
                <img src={imgSrc} alt='' />
              </article>
            ))}
          </section>
        )}
        {!friends ? <p>Loading..</p> : (
          <aside>
            <ul>
              {friends
                .sort((a, b) => (a.isOnline && !b.isOnline ? -1 : 0))
                .map(({ id, name, isOnline }) => (
                  <li key={id} className={isOnline ? 'online' : 'offline'}>
                    {name}
                  </li>
                ))}
            </ul>
          </aside>
        )}
      </div>
    </div>
  );
}

useEffect(() => {
  const handleMove = (event) => ...

Why is an event handler being defined in useEffect()?

Perhaps it has to do with the fact that this particular useEffect is being called with an empty dependency array. This means that the effect doesn’t get called after every render. The effect is only called once i.e. after the first render. Similarly, the cleanup function is also called once i.e. after the last render. Since the handleMove event handler is not being used elsewhere and the useEffect is only going to get triggered just once, so the definition of the event handler is not going to happen multiple times. Packaging the definition with the effects works adequately for this particular case. If the dependency array was omitted or a non-empty dependency array was used, then defining the event handler within the useEffect would not be suitable because the useEffect would be triggered multiple times.