React lifecycle methods with hooks cheatsheet for everybody

This article was originally published at:
https://www.blog.duomly.com/react-lifecycle-methods-with-hooks-cheatsheet/


Intro to React lifecycle methods

Welcome to the react lifecycle tutorial, where I will explain all the things related to the react component lifecycle methods.

You’ll learn about the four main react component lifecycle stages, when they’re fired, and what is happening inside.

Next, we will talk about the methods used during these stages, which ones we need, and which ones we should avoid.

We won’t forget about these deprecated methods, so you will know which ones you should definitely refactor in your code and don’t use anymore.

Finally, in the last step, we will talk about react lifecycle hooks, and I’ll tell you how we can implement them to replace all of the lifecycle methods when we build reactjs functional components.

Let’s start!

And if you prefer video, here is the youtube version where I explain all of that:

React lifecycle diagram

React lifecycle diagram

In React, we have four main lifecycle phases.

Actually, I’d say there are three lifecycle phases and one phase for Error Handling, which I will tell you about a bit later.

Now, let’s focus on these three most popular and mostly used stages.

Anyway, even if not every developer cares about that stage, I still think it should be changed, and error handling should be implemented into every project because it can help us save a lot of time in the future.

So in the image, you can see the diagram containing the three life cycle stages: Mounting, Update and Unmounting.

The first two, I mean Mount and Update stage, are split into three phases: render, pre-commit, and commit.

The first phase of Mount and Update, called Render, happens when we do the pure rendering. Our DOM is not touched yet. We can stop or restart this phase until it is finished.

The second one, named Pre-Commit, is when we already have the first possibility of reading DOM by React app.

And the last one, named Commit, is when we have ready interaction with DOM, can manipulate Document Object Model, create side effect, and want to touch stuff outside our instance (component) like, for example, data fetching we can plan updates.

React Mount

Mount phase is the initial stage of the React component lifecycle and the moment when React creates our components and inserts them into the DOM.

Let’s see the component mount methods.

You will learn about when they’re fired, their responsibility, and when it is good to avoid using them.

React constructor

It’s a component lifecycle method that is fired before the react component is mounted.

Constructor is useful when we need to init components state, bind functions, or event handlers in our component.

We always need to remember to call super(props) to avoid situations when our component’s props are undefined.

React static getDerivedStateFromProps

This method is used in Mount and Update lifecycle.

This component lifecycle method is called just before the render method in both cases, mounting and updating.

It’s handy when we would like to change our component’s internal state by recognizing the props’ change implemented into the component.

Anyway, it’s not an easy method to use. You need to know how to do it. It will be much easier to use componentDidUpdate or memoization (ensuring our value in the render is recompiled when the inputs value change), but not in every case.

React render

This method is used in Mount and Update lifecycle, and it’s the only required method in the react component.

In react component lifecycle order, it’s called after getDerivedStateFromProps during the Mount cycle, or after shouldComponentUpdate and forceUpdate methods in Update cycle, new props or new components state will fire render method as well.

Render shouldn’t modify state and should just return elements like react elements, arrays, portals, string or numbers, and booleans or null, shortly it’s used mostly for creating or returning elements.

The returned value can be defined or can depend on component props or component state.

Interestingly, we can stop rendering component by returning false in function shouldComponentUpdate, and oppositely, we can force component to rerender by calling method forceUpdate.

React componentDidMount

This component lifecycle method is called after a component is mounted, like put into the DOM tree.

It’s used mostly for DOM operations, subscriptions, or data fetching, so it’s an excellent place to add all the data fetch actions, such as setState methods.

Anyway, you need to know that the component will rerender if you change state, but still before the browser will update the screen.

React componentWillMount

React componentWillMount is the deprecated method, which means you should refactor it to avoid future problems.

React update lifecycle methods

The update stage is the second phase of the React component lifecycle.

It means it can happen when the React application changes the props passed into the component’s component or internal state.

In the case of update, React calls methods in order as below:

static getDerivedStateFromProps
shouldComponentUpdate 
render 
getSnapshotBeforeUpdate 
componentDidUpdate

Now, let’s see what each of them does (getDerivedStateFromProps and render methods were described in the Mount section).

React shouldComponentUpdate

This method is always called when a state or props changed.

Fires before render methods, and what is more interesting, this method doesn’t fire when we use method forceUpdate.

React shouldComponent update method works like, if it returns true (that is the default value), React component will rerender, but if it returns false, component will not render again.

Used mostly for improving performance, to check if rerender is definitely necessary, and stop it when it’s not.

One more thing that you should know about that method is that you can use PureComponents instead of messing with this function because React PureComponent has built-in comparison and will not rerender when not necessary.

React getSnapshotBeforeUpdate

React getSnaphostBeforeUpdate is fired after, or I’d say during render method, just before render will update DOM.

It’s not very popular to use, and it’s used only in exceptional cases, for example, news feeds with infinite scrolls.

React componentDidUpdate

This method is very similar to the componentDidMount, and it’s fired after the finished render method, but in the Update stage of React component lifecycle.

Anyway, it’s not called after the initial render, which is called in the Mount stage of the React component lifecycle.

As well as the componentDidMount, it’s used mostly for DOM operations or data fetching.

React componentWillUpdate (deprecated)

React componentWillUpdate is the deprecated method, which means you should refactor it to avoid future problems.

React componentWillReceiveProps (deprecated)

React componentWillReceiveProps is the deprecated method, which means you should refactor it to avoid future problems.

React Unmount

It’s the last stage of the React component lifecycle.

Unmounting is when a component is being removed from the Document Object Model (DOM), and it has only one method called during this stage, the componentWillUnmount.

React componentWillUnmount

It’s the only method called during the unmount stage, and it’s called precisely before a component is unmounted and destroyed.

Like the componentDidMount, it’s used mostly for DOM operations or data fetching, but in this case, we use that method to clean all of the changes, listeners, or subscriptions that we created in componentDidMount or componentDidUpdate methods.

React Component Error Handling

Error handling is the lifecycle stage that I wouldn’t name lifecycle, more like exception handler, but still is one of the most crucial parts in the component lifecycle.

This part is responsible for properly handling errors during rendering, calling constructor, or another part of the lifecycle method.

Proper error handling is very important for every React (and every other) application and always should be done carefully because it will save us tons of time and maybe even more good mood in the future.

We have two methods possible to fire in this phase, static getDerivdedStateFromError, and componentDidCatch.

React static getDerivedStateFromError

React static getDerivedStateFromError is the method that is fired when our component throws an error.

We should use it to take the error as a param and change the state to the component.

Next, we can see in the UI about something went wrong.

React componentDidCatch

This method works a bit differently than componentDidCatch because it takes the two params, one is an error, and the second one is info, which shows which part of the application created an error.

It’s useful when we have detailed logs and will use this method to pass information to the logs that we can monitor as the developer or admin.

React lifecycle hooks

All of the react component lifecycle stages help us handle most of the moments precisely and perform actions that we need at that moment, but not always we need them.

In many applications, we will need to catch only moments when we init component, update, and unmount, without going for all of the small parts.

In this case, we can replace most of that with a useEffect hook.

useEffect hook explanation

React useEffect hook can be used as a successful replacement for componentDidMount, componentDidUpade, and componentWillMount.

It’s named useEffect from the name of all of the actions that we performed out of the instance (side-effects).

We can fire useEffect like componentDidMount and componentDidUpdate:

useEffect(()=>{
  //some logic here
});

In this case, the useEffect hook will start on both actions and fire when the component inits or changes state.

We can fire useEffect like componentDidMount only:

useEffect(()=>{
  //some logic here
},[]);

In this case, the useEffect hook will start only the first time, like in the Mount phase.

We can fire useEffect like componentDidUpdate related to the one part of the instance only:

useEffect(()=>{
  //some logic here
},[name]);

In this case, the useEffect hook will start only when the state “name” will be changed.

We can fire useEffect like componentWillUnmount:

useEffect(()=>{
  listen();
  return function cleanup() {
    stopListening();
  }
});

In this case, the useEffect hook will start on the init, start function listen, and when a component will go into unmounting, useEffect will start function cleanup.

Summary of react lifecycle methods

Congratulations, now you know all about the react component lifecycle!

You’ve learned about how to use hooks to simplify your work with lifecycle as well.

It is a long lesson and full of knowledge, but I’m sure now your code will look better, and you will have real deep-inside knowledge about how react components work during their lifecycle.

It’s definitely not something that every beginner should know, but experienced developers must have this knowledge to avoid future mistakes.

Let us know in the comments what topic is the most interesting for you and what you would like to learn now!

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Radek from Duomly

#react #javascript #web-development #html #css

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React lifecycle methods with hooks cheatsheet for everybody
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Autumn Blick

1598839687

How native is React Native? | React Native vs Native App Development

If you are undertaking a mobile app development for your start-up or enterprise, you are likely wondering whether to use React Native. As a popular development framework, React Native helps you to develop near-native mobile apps. However, you are probably also wondering how close you can get to a native app by using React Native. How native is React Native?

In the article, we discuss the similarities between native mobile development and development using React Native. We also touch upon where they differ and how to bridge the gaps. Read on.

A brief introduction to React Native

Let’s briefly set the context first. We will briefly touch upon what React Native is and how it differs from earlier hybrid frameworks.

React Native is a popular JavaScript framework that Facebook has created. You can use this open-source framework to code natively rendering Android and iOS mobile apps. You can use it to develop web apps too.

Facebook has developed React Native based on React, its JavaScript library. The first release of React Native came in March 2015. At the time of writing this article, the latest stable release of React Native is 0.62.0, and it was released in March 2020.

Although relatively new, React Native has acquired a high degree of popularity. The “Stack Overflow Developer Survey 2019” report identifies it as the 8th most loved framework. Facebook, Walmart, and Bloomberg are some of the top companies that use React Native.

The popularity of React Native comes from its advantages. Some of its advantages are as follows:

  • Performance: It delivers optimal performance.
  • Cross-platform development: You can develop both Android and iOS apps with it. The reuse of code expedites development and reduces costs.
  • UI design: React Native enables you to design simple and responsive UI for your mobile app.
  • 3rd party plugins: This framework supports 3rd party plugins.
  • Developer community: A vibrant community of developers support React Native.

Why React Native is fundamentally different from earlier hybrid frameworks

Are you wondering whether React Native is just another of those hybrid frameworks like Ionic or Cordova? It’s not! React Native is fundamentally different from these earlier hybrid frameworks.

React Native is very close to native. Consider the following aspects as described on the React Native website:

  • Access to many native platforms features: The primitives of React Native render to native platform UI. This means that your React Native app will use many native platform APIs as native apps would do.
  • Near-native user experience: React Native provides several native components, and these are platform agnostic.
  • The ease of accessing native APIs: React Native uses a declarative UI paradigm. This enables React Native to interact easily with native platform APIs since React Native wraps existing native code.

Due to these factors, React Native offers many more advantages compared to those earlier hybrid frameworks. We now review them.

#android app #frontend #ios app #mobile app development #benefits of react native #is react native good for mobile app development #native vs #pros and cons of react native #react mobile development #react native development #react native experience #react native framework #react native ios vs android #react native pros and cons #react native vs android #react native vs native #react native vs native performance #react vs native #why react native #why use react native

What are hooks in React JS? - INFO AT ONE

In this article, you will learn what are hooks in React JS? and when to use react hooks? React JS is developed by Facebook in the year 2013. There are many students and the new developers who have confusion between react and hooks in react. Well, it is not different, react is a programming language and hooks is a function which is used in react programming language.
Read More:- https://infoatone.com/what-are-hooks-in-react-js/

#react #hooks in react #react hooks example #react js projects for beginners #what are hooks in react js? #when to use react hooks

Using React Hooks instead of lifecycle methods

How to replace React lifecycle methods with React Hooks in functional components? First, let’s see to lifecycle methods diagram.

Image for post

You don’t need the constructor method in functional components. Use the [useState](https://reactjs.org/docs/hooks-state.html)Hook to initialize the state.

The common React component lifecycle methods arecomponentDidMount,``componentDidUpdate and componentWillUnmount. For all cases we should use the [useEffect](https://reactjs.org/docs/hooks-effect.html)Hook. Let’s see an example for details.

//componentDidMount and componentDidUpdate. An effect re-runs every render

	useEffect(() => {
	    // to do smth...
	})

	//componentDidMount. An effect runs only on mount

	useEffect(() => {
	    // to do smth...
	}, [])
view raw
demo.tsx hosted with ❤ by GitHub

For componentWillUnmount method, we should add the return statement to the useEffect Hook.

useEffect(() => {
	  // to do smth...

	  return () => {
	    // to do smth else when a component is unmounted...
	  }
	})
view raw
demo.tsx hosted with ❤ by GitHub

#react-lifecycle #react #react-hook

Hayden Slater

1599277908

Validating React Forms With React-Hook-Form

Validating inputs is very often required. For example, when you want to make sure two passwords inputs are the same, an email input should in fact be an email or that the input is not too long. This is can be easily done using React Hook From. In this article, I will show you how.

Required Fields

The most simple, yet very common, validation is to make sure that an input component contains input from the user. React Hook Form basic concept is to register input tags to the form by passing register() to the tag’s ref attribute. As we can see here:

#react-native #react #react-hook-form #react-hook

The Ugly Side of React Hooks

In this post, I will share my own point of view about React Hooks, and as the title of this post implies, I am not a big fan.

Let’s break down the motivation for ditching classes in favor of hooks, as described in the official React’s docs.

Motivation #1: Classes are confusing

we’ve found that classes can be a large barrier to learning React. You have to understand how "this"_ works in JavaScript, which is very different from how it works in most languages. You have to remember to bind the event handlers. Without unstable syntax proposals, the code is very verbose […] The distinction between function and class components in React and when to use each one leads to disagreements even between experienced React developers._

Ok, I can agree that

thiscould be a bit confusing when you are just starting your way in Javascript, but arrow functions solve the confusion, and calling a_stage 3_feature that is already being supported out of the box by Typescript, an “unstable syntax proposal”, is just pure demagoguery. React team is referring to theclass fieldsyntax, a syntax that is already being vastly used and will probably soon be officially supported

class Foo extends React.Component {
  onPress = () => {
    console.log(this.props.someProp);
  }

  render() {
    return <Button onPress={this.onPress} />
  }
}

As you can see, by using a class field arrow function, you don’t need to bind anything in the constructor, and

this will always point to the correct context.

And if classes are confusing, what can we say about the new hooked functions? A hooked function is not a regular function, because it has state, it has a weird looking

this(aka_useRef_), and it can have multiple instances. But it is definitely not a class, it is something in between, and from now on I will refer to it as aFunclass. So, are those Funclasses going to be easier for human and machines? I am not sure about machines, but I really don’t think that Funclasses are conceptually easier to understand than classes. Classes are a well known and thought out concept, and every developer is familiar with the concept ofthis, even if in javascript it’s a bit different. Funclasses on the other hand, are a new concept, and a pretty weird one. They feel much more magical, and they rely too much on conventions instead of a strict syntax. You have to follow somestrict and weird rules, you need to be careful of where you put your code, and there are many pitfalls. Telling me to avoid putting a hook inside anifstatement, because the internal mechanism of hooks is based on call order, is just insane! I would expect something like this from a half baked POC library, not from a well known library like React. Be also prepared for some awful naming like useRef (a fancy name forthis),useEffect ,useMemo,useImperativeHandle(say whatt??) and more.

The syntax of classes was specifically invented in order to deal with the concept of multiple instances and the concept of an instance scope (the exact purpose of

this ). Funclasses are just a weird way of achieving the same goal, using the wrong puzzle pieces. Many people are confusing Funclasses with functional programming, but Funclasses are actually just classes in disguise. A class is a concept, not a syntax.

Oh, and about the last note:

The distinction between function and class components in React and when to use each one leads to disagreements even between experienced React developers

Until now, the distinction was pretty clear- if you needed a state or lifecycle methods, you used a class, otherwise it doesn’t really matter if you used a function or class. Personally, I liked the idea that when I stumbled upon a function component, I could immediately know that this is a “dumb component” without a state. Sadly, with the introduction of Funclasses, this is not the situation anymore.

#react #react-hooks #javascript #reactjs #react-native #react-hook #rethinking-programming #hackernoon-top-story