DEV Community

React useEffect Guides

The useEffect Hook lets you perform side effects in your components.

This is a collection of top and trending guides written by the community on subjects related to React useEffect concepts. For all things React, check out the React tag! Please contribute more posts like this to help your fellow developer in need.

React useEffect cleanup: How and when to use it

The useEffect hook is built in a way that if we return a function within the method, this function will execute when the component gets disassociated. This is very useful because we can use it to remove unnecessary behavior or prevent memory leaking issues.

What is useEffect hook and how do you use it?

A hook is a function which enables you use state and other react features without writing ES6 classes.

useEffect hook is part of the react hooks API. If you are familiar with react life cycles, useEffect hook is equivalent to life cycle methods componentDidMount, componentDidUpdate and componentWillUnmount combined. In fact, according to the React documentation on Hooks, useEffect hook was developed to address some of the challenges posed by life cycle methods of ES6 class components. Since this post is about what effect hook is and how it is used, i won't go into why it was developed. You can look at it Here.

In React functional components, we perform side effects such as fetching data from an API or manually updating the DOM inside the useEffect hook.

Ways to Handle Deep Object Comparison in useEffect hook

In React, side effects can be handled in functional components using useEffect hook. In this post, I'm going to talk about the dependency array which holds our props/state and specifically what happens in case there's an object in this array.

Optimize useEffect by using a condition as a dependency

The useEffect hook is a great way to wrap side effects since the release of React 16.8. To quickly recap, this hook allows you to create functional components with behaviour akin to React classes' componentDidMount and componentDidUpdate.

How to make sure useEffect catches array changes

There is a way to use useEffect to only run when variables provided in a second argument are updated, like this:

6 use cases of the useEffect ReactJS hook

Whenever we need to make use of side effects in our application, useEffect is the way to go. This hook doesn't present many complications, except for non-primitive data types, due to how JavaScript handles them.

Setting state for parent from within useEffect hook in child component causes an infinite loop

That's exactly what I have found recently.

Let's say we have a parent and a child and we pass setState function to the child in order to it can set state for parent from within a useEffect hook inside child component. This scenario will cause an infinite loop no matter what you put in the dependencies' second argument array of useEffect hook.

Let's say what in my opinion happens. setState causes the parent to re-render because we are updating its state. But this implies a render of the child. And I say render and not re-render because when parent re-renders, for useEffect hook is like rendering of the child was first render, and that's why no matter what you put on the dependencies array it will always execute its side effect, setting state for parent and initiating a new loop, that will continue forever.

So when you lift the state up in React.js you must take care not to call setState or dispatch (this applies as well to useReducer) inside a useEffect hook from within a child component.

Here, I show you the code:

React Native Hooks , How To Use useState and useEffect Example

But Now each time when any of state is updated, this hook method is calling.

but we need to call this only at component will mount and unmount. So how can we fix it?

Simply, you can pass the empty array as a second argument. By doing this, this useEffect will call only at the component mount and unmount.

setTimeOut in useEffect API call (Data Fetching).

Fetching API data with useEffect can be tricky sometimes. In this article, we will look at one trick for efficient data fetching with useEffect.

How to cancel all subscriptions and asynchronous tasks in a useEffect cleanup function?

Even if the component is unmounted, useEffect will try to maintain contact with your data-fetching function. Because this is an anti-pattern that exposes your app to memory leaks, canceling your useEffect subscription optimizes your app.

How to replace component lifecycle with useEffect hook in React?

Before React 16.8, we were forced to use the class-based component to have access in component lifecycle. And now with Hooks, we are now able to use functional component for state management, data fetching etc. We can now replace component lifecycle like componentDidMount, componentDidUpdate and componentWillUnmount with useEffect in our React component.

React: useEffect explained with lifecycle methods

React's useEffect hook combines componentDidMount, componentDidUpdate and componentWillUnmount lifecycle methods. This is very useful for the following reasons: it reduces the amount of code, simplifies the code and allows for multiple useEffect hooks to be called in a single component.

Cleaning up Async Functions in React's useEffect Hook (Unsubscribing)

While all these are beautiful, there is a little caveat (or maybe not) that is a little bit frustrating when working with useEffect hook.

Animation Classes & useEffect Hooks - Is There a Better Way?

If you want to see the issue, comment out the useEffect hook and you will see that it fades out, then comes right back into view!

Dealing with infinite loops in useEffect hook

"ESLint: React Hook useEffect has missing dependencies: 'body', 'dispatch', 'headers', 'method', 'url', and 'user.jwt'. Either include them or remove the dependency array.(react-hooks/exhaustive-deps)"

My approach to SSR and useEffect - discussion

I've put all data fetching in useEffect hook - pretty standard approach. However, useEffect does not play very well with server-side rendering. I've managed to work this out by creating custom hook useSSE - "use server-side effect" and I've created an npm package from it.

Run Function after useEffect to Manipulate Data?

I'm using the OpenWeather REST API which comes in JSON format. I know I have to make my fetch,(Axios in my case) call inside the useEffect because the component needs to render first, then calls the REST endpoint.

Understanding React's useEffect Hook

If you haven’t learned Hooks yet, you should do it as soon as possible. And if you’ve been reading about them, you may be a bit confused about the useEffect Hook 😕

Connect useEffect and useState to Update Components with Data

Our useEffect connects us to the outside world — fetching data with JavaScript.

The callback we give to fetchPokemon calls our useState updater function when data is ready — updating our component.

useState and useEffect in React

The useEffect hook is the combination of componentDidMount(run only once when the component is inserted into the DOM tree structure) componentDidUpdate(run something on each render), and componentWillUnmount (run when the component will be removed from the DOM tree) class lifecycle methods.

How to Fix useEffect Hook executing in an endless loop?

Using useEffect Hook, tells React that your component needs to do something after render. React will remember the function you passed and call it later after performing the DOM updates.

useUpdateEffect: useEffect that doesn't trigger on mount

The code behind it is very simple. It only takes a useRef, to keep track of the initial render, and a useEffect with a guard to check whether if it's the first mount or not:

ทำความเข้า useEffect ตั้งแต่เริ่มต้น

⚛️ React ไปวันๆ EP.2 - ทำความเข้า useEffect ตั้งแต่เริ่มต้น

useState && useEffect ⚛

As we know, use effect is basically used to perform side Effect (API request). So it's obvious that we will make our API request in the useEffect function.

React - useEffect hook - A Quick Guide

The useEffect hook receives two parameters: one function to be executed and an array of dependencies.

using useEffect effectively

I started exploring react's functional component and really like how it has made the code neat and compressed the component to a few lines. We are going to discuss 3 most used scenarios there must be more where you can make use of useEffect hook. In this article, I'll be comparing useEffect with classical component hooks and explaining the whys and hows. So yeah here's the list of use cases.

Mastering the useEffect API

The Hooks API is a great feature that was added in version v16.8 last february and change the way on how we write our React Apps. We now write more functional components instead of class components. We don't need to bind any more functions inside the constructor because of the functional components. So today we demystify the useEffect API.

React's useEffect Hook

Gladly, I understood it, and I now want to show you what useEffect is and how you can use it.

React: useEffect vs useLayoutEffect

If you have just started working on React or have ever written a functional component, I am pretty sure that you may have come across useEffect hook and you may know that it is used to perform some side effects like data fetching, sending HTTP requests, etc. But in this post we will talk about another react hook called useLayoutEffect and see how it is different from useEffect hook.

Docs are boring, let's build a movie finder app to learn React hooks (useReducer, useEffect and useContext)

The useEffect hook takes two arguments:

The useEffect Cheatsheet

Now I want to share my mental model in this small cheat sheet to help you learn useEffect better or own a better mental model.

What is useEffect Hook in ReactJS?How useEffect works and where to use it?

UseEffect? What is syntax ? How does it work? When to use it ? And Some common use cases of useEffect Hook.

Run useEffect Only Once :React

Alt Text

If you want to run an effect and clean it up only once (on mount and unmount), you can pass an empty array ([]) as a second argument. This tells React that your effect doesn’t depend on any values from props or state, so it never needs to re-run. This isn’t handled as a special case — it follows directly from how the dependencies array always works.

If you pass an empty array ([]), the props and state inside the effect will always have their initial values. While passing [] as the second argument is closer to the familiar componentDidMount and componentWillUnmount mental model, there are usually better solutions to avoid re-running effects too often. Also, don’t forget that React defers running useEffect until after the browser has painted, so doing extra work is less of a problem.

Intro to React useEffect Hook

React useEffect is an alternative to the "old" class lifecycle methods/hooks.

React useEffect cleanup

React's useEffect hook is a super hook to run side effects.

You might be wondering what kind of side effects we could be talking about?

React Hooks: useEffect Explained in 5 Minutes

When building a React app, there will be times where we want to run a piece of code after a component is rendered (think fetching data from an api as one example) — the useEffect React Hook will help us accomplish that.

React useEffect ¿Por que el arreglo de dependencias es importante?

React useEffect es quizá el hook que más confusiones genera a la hora de utilizarlo.

Algunas de esas confusiones se debe al intento de comparar su funcionamiento con los estados del ciclo de vida de un componente de clase, algo que aclaro en este post anterior

Understanding the flow of React's useEffect hook

React's useEffect hook is used quite often in applications. It is used to perform side effects in your components like subscribing/unsubscribing to events, making API requests etc.

React: Guia Visual para o Modelo Mental do React, Parte 2 - useState, useEffect e ciclos de vida

O React consegue fazer isso acompanhando cada componente e a ordem em que cada hook é declarado. Essa é a razão pela qual você não pode ter um React Hook dentro de uma condicional. Se useState, useEffect ou qualquer outro hook for criado condicionalmente , o React não poderá controlá-lo adequadamente.

React 18 useEffect Double Call for APIs: Emergency Fix

Another fix is to use an AbortController to terminate the request from the first useEffect . Let’s say this is your code:

Intro to React's useEffect Hook

"If you’re familiar with React class lifecycle methods, you can think of useEffect Hook as componentDidMount, componentDidUpdate, and componentWillUnmount combined."

Manage server state with useEffect hook

Alt Text

Figure 3: The parameters of the useEffect hook.

Why use useEffect when logging?

Why should I use useEffect when console.log even it works well without, after rendering?

How to useEffect vs componentDid/Will-unmount

I was working on a project and I had to close out some modals, and realized there were both Class component modals and Functional component modals that were involved... so I decided for the class component I would use the life cycle methods and use useEffect for the functional components heres what they look like

useMountedEffect: asynchronous useEffect on potentially unmounted components

When we use effects, or more precisely the useEffect hook, than because very often we do want to execute something asynchronously. In most scenarios we are doing this when a component gets mounted.

React's useEffect and useRef Explained for Mortals

I’ve certainly fallen victim to this many, many times. Particularly with useEffect. Before we dive into this particular hook, let me say that I love writing React with hooks and wouldn’t want to go back to classes. That said, useEffect is a big pain point.

Happy React useEffect coding!