Learn React Hooks In 6 Minutes

Summary

This video script discusses the evolution of React.js from class components to functional components with hooks. It explains how React hooks, introduced in version 16.8, enable state management and lifecycle handling in functional components. The tutorial demonstrates converting a class component to a functional one using useState and useEffect hooks, highlighting the benefits and efficiency of the new approach. The speaker also mentions plans for future videos on hooks' advantages and creating custom hooks.

Takeaways

• 🚀 React has evolved to favor function components over class components for simpler and more modern code.
• 🔄 React Hooks, introduced in React 16.8, are the solution to managing state and replacing lifecycle methods in function components.
• 🎯 The `useState` hook allows function components to maintain and update state without the need for a class component's `this.setState`.
• 🔧 Multiple pieces of state can be managed in a function component by using `useState` multiple times, each creating its own state variable and updater function.
• 🔏 The `useEffect` hook can be used to replicate the behavior of lifecycle methods like `componentDidMount`, `componentDidUpdate`, and even `componentWillUnmount`.
• 💡 By passing an empty array to `useEffect`, the function inside runs only once, similar to `componentDidMount`, while the lack of an array triggers the function on every render.
• 🛠 To persist state across page refreshes or visits, `useEffect` can be used to save and retrieve state from local storage, updating the component's state accordingly.
• 📌 React Hooks promote a more declarative programming approach, focusing on reacting to data changes rather than component lifecycle events.
• 📈 Using hooks can lead to more concise and potentially less error-prone code, as it abstracts away some of the complexities of class components.
• 🔜 Future React tutorials will increasingly focus on the use of hooks, reflecting the shift in best practices within the React community.
• 🤖 Creating custom hooks is a powerful feature that allows for the abstraction of reusable logic and state management patterns across different components.

Q & A

What has changed in React since the introduction of class components?

React has evolved to favor the use of function components over class components. This shift has led to the introduction of React Hooks, which allow for state management and lifecycle handling in function components, replacing the need for class component methods like 'this.setState' and lifecycle events like 'componentDidMount' and 'componentDidUpdate'.

What are React Hooks and when were they introduced?

React Hooks are a feature introduced in React version 16.8 that enables developers to use state and other React features without writing class components. Hooks provide a way to manage state and side effects in function components, making them more powerful and flexible.

How does the 'useState' hook work in function components?

The 'useState' hook is used to manage state in function components. It returns an array with two elements: the first is the current state value, and the second is a function to update that state. Optionally, an initial state value can be provided. In the script, 'useState' is used to manage the text displayed and the count of button clicks.

How can you handle component lifecycle events using React Hooks?

The 'useEffect' hook is used to handle lifecycle events in function components. It accepts a function that contains the side effects you want to occur during the lifecycle of the component. By passing an empty array as the second argument to 'useEffect', the function will only run once, similar to 'componentDidMount'. If you want to run the function whenever a specific state changes, you include that state variable in the array.

What is the role of the 'useEffect' hook in replacing lifecycle methods?

The 'useEffect' hook replaces the need for lifecycle methods by allowing you to specify when you want certain side effects to happen. For example, you can replicate the behavior of 'componentDidMount' by running code in 'useEffect' with an empty array as the second argument. This makes it clear that the code should run once, when the component first mounts.

How can you save and retrieve state between component mounts using 'useEffect' and local storage?

By using 'useEffect' with an empty array as the second argument, you can save the state to local storage when the component mounts. This ensures that the state is persisted even when the component unmounts and remounts. To retrieve this state on initial mount, you check local storage and set the state accordingly within the 'useEffect' hook.

What is the significance of the 'useEffect' hook in managing side effects?

The 'useEffect' hook is significant because it provides a consistent and centralized way to manage side effects in function components. It allows developers to react to state changes and perform necessary actions, such as updating the DOM, fetching data, or interacting with other APIs, all in a clean and organized manner.

How does the 'useEffect' hook differ from 'componentDidUpdate'?

While 'componentDidUpdate' is a lifecycle method that runs after updates to the component, 'useEffect' is a hook that can be used to handle similar behavior. 'useEffect' runs after every render by default, but you can control its behavior by providing a specific array as the second argument to the hook. This allows you to run code only when certain variables change, similar to the 'componentDidUpdate' method.

What is the role of the second argument in the 'useEffect' hook?

The second argument to 'useEffect' is an array that determines when the function provided as the first argument should run. If no array is provided, the function will run after every render. If an empty array is provided, the function will run once, on mount. If the array contains specific variables, the function will run only when those variables change.

How can you create a custom hook in React?

Custom hooks can be created in React by encapsulating a piece of state logic or side effect within a function that returns one or more hooks. These custom hooks can then be reused across different components, promoting code reuse and cleaner component structures.

What are the benefits of using React Hooks in function components?

React Hooks provide several benefits, including simpler and more readable code by eliminating the need to create class components with lifecycle methods, better reusability of logic through custom hooks, and improved performance through more granular control over when effects run.

Why is the mindset shift when using React Hooks important?

The mindset shift when using React Hooks is important because it encourages developers to think in terms of data changes and their effects, rather than component lifecycles. This leads to more maintainable and efficient code, as well as easier debugging and understanding of how components behave in response to state changes.

Outlines

00:00

🚀 Introduction to React Hooks and State Management

This paragraph introduces the evolution of React and the transition from class components to functional components. It explains that with functional components, developers lose the traditional ways of state management using 'this.setState' and lifecycle methods. The paragraph then introduces React Hooks as the solution, which were first introduced in React version 16.8. The speaker plans to cover state management in this video and lifecycle methods in a future one, emphasizing the importance of understanding hooks as future tutorials will focus on their usage. The paragraph also provides a brief example of converting a class component to a functional component using hooks.

05:02

🔄 Implementing State Management with useState

This paragraph delves into the specifics of using the 'useState' hook for state management in functional components. It describes how to convert a class component that updates text on button click into a functional component using 'useState'. The paragraph explains the process of removing class methods and constructor, and using the 'useState' hook to create and update state. It also demonstrates how to add additional state for counting button clicks and how to display this state. The speaker highlights the shift in mindset required when using hooks, moving from thinking about components as having life cycles to reacting to data changes.

Keywords

💡React

React is an open-source JavaScript library used for building user interfaces, particularly single-page applications. It is developed and maintained by Facebook. In the video, React is the primary focus, discussing the transition from class components to functional components and the introduction of React Hooks to manage state and lifecycle in a more efficient way.

💡Class Components

Class Components in React are a way of creating components using JavaScript classes. They have a more traditional object-oriented approach, with methods and a constructor. The video explains that class components have been largely replaced by functional components as the preferred way to write React applications, due to the introduction of React Hooks.

💡Functional Components

Functional Components in React are components that are defined as plain JavaScript functions instead of classes. They do not have their own state or lifecycle methods as class components do. The video emphasizes the shift towards using functional components, which are considered more modern and easier to understand and maintain.

💡React Hooks

React Hooks are a feature introduced in React 16.8 that allows state and lifecycle logic to be used in functional components. Hooks are essential in the video's narrative as they are presented as a solution to manage state and handle lifecycle events without the need for class components.

💡useState

useState is a built-in hook in React that adds state to functional components. It returns an array with two elements: the current state value and a function to update it. In the video, useState is used to manage the text state and the count state, demonstrating how to handle state changes in functional components.

💡useEffect

useEffect is a built-in hook in React that replaces the lifecycle methods of class components, such as componentDidMount and componentDidUpdate. It is used to perform side effects in functional components, such as fetching data, updating the DOM, or subscribing to events. The video illustrates how useEffect can be used with different scenarios, including running code on component mount, update, or unmount.

💡Lifecycle Methods

Lifecycle Methods in React are methods that are called at different points in a component's life, such as when it is mounted, updated, or unmounted. The video discusses how React Hooks, particularly useEffect, can replace these methods, allowing functional components to have the same capabilities as class components.

💡Local Storage

Local Storage is a web storage mechanism that allows data to be stored in a key-value pair format on the client-side. In the video, local storage is used to persist the count state across page reloads or visits, demonstrating how React Hooks can interact with the browser's storage API.

💡Component Mount

Component Mount refers to the process of initializing a React component and rendering it to the DOM for the first time. The video explains how the useEffect hook can be used to run code only once, when the component mounts, similar to the componentDidMount lifecycle method in class components.

💡State Management

State Management in React refers to the process of handling and updating the data that affects the component's behavior and rendering. The video demonstrates how state management has evolved from using this.setState in class components to using the useState hook in functional components.

💡Web Application Programming

Web Application Programming involves creating applications that run in a web browser, using languages like HTML, CSS, and JavaScript. The video discusses a shift in mindset for web application programming with the introduction of React Hooks, focusing on reacting to data changes rather than component lifecycles.

Highlights

React has evolved from class components to function components.

Function components are now more common in React, simplifying the way developers write components.

React Hooks were introduced in React version 16.8, offering a new way to manage state and replace lifecycle methods.

The classic way of holding state using `this.setState` is replaced with the `useState` hook in function components.

Lifecycle methods such as `componentDidMount` and `componentDidUpdate` are replaced with the `useEffect` hook.

The `useState` hook allows for state management in function components by providing a state value and a function to update it.

Multiple states can be managed in a function component by using `useState` multiple times for different pieces of state.

The `useEffect` hook can be used to perform side effects, such as fetching data or saving to local storage, in response to state changes.

An empty array as the second argument to `useEffect` ensures the function runs only once, similar to `componentDidMount`.

By including specific state variables in the second argument of `useEffect`, the function will run only when those variables change.

The `useEffect` hook can be used to persist state across page refreshes by interacting with local storage.

The new way of handling state and lifecycle with hooks promotes a more declarative and efficient approach to component development.

The upcoming React tutorials will focus on using React Hooks, emphasizing their importance in modern React development.

The presenter plans to create more content on the benefits of hooks and how to create custom hooks.

Using hooks can lead to writing less code while maintaining the same level of functionality and interactivity in React applications.

The shift to hooks requires a change in mindset from thinking about components as having life cycles to reacting to data changes.

Hooks provide a more powerful and flexible way to handle state and side effects in React, enhancing the development experience.

Transcripts

hey everyone so in my older react

tutorials I used class components and

just generally old-school practices

since then react has evolved quite a bit

instead of writing class components it's

now more common to use function

components and when you use function

components you lose the classic way of

holding state using this set state and

you also lose lifecycle methods and

these are methods such as component did

mount and component did update so if the

new way of writing react components

forgoes these things how can you hold

state and how can you handle component

changes in react the answer is react

hooks react hooks were introduced in

version 16.8 of react and as of this

recording

we're on sixteen point thirteen point

one I'm gonna start off by talking about

how to manage state and then I'll talk

about how to replace the lifecycle

methods in another video talk more about

the benefits of hooks and also even how

to create your own hooks this video is

going to be an important one because my

future react tutorials are going to be

using react hooks from now on but first

go ahead and hit the subscribe button if

you haven't already so you don't miss

any of my future videos and while you're

there go ahead and hit the thumbs up so

that my video will reach more people

let's go ahead and get started the best

way to explain this is probably to take

a classic react class component and then

convert it to the new function way so

let's go ahead and do that so here we

have a react component that updates text

when a button is clicked as you can see

we are rendering some JSX that contains

a button and this button has an on click

function that calls this set state and

updates the text inside of the div above

this button we are simply rendering the

text that's currently in state so when

the state updates our text will update

as well as you can see when I click the

button you can see the text now updates

this is a very simple example but it

shows the power of react you see one of

the things that makes react so powerful

is how simple it makes it for us to

react to state changes or componentry

renders so let's convert this component

to a function component that uses hooks

I'll start by changing the class

declaration to a function now obviously

we can't use class methods inside of a

plain JavaScript function like this so

we need to remove constructor and render

notice how I kept the return portion

when creating a function component in

react we want to return JSX each time

this function runs it will rerender the

component on the screen now if I tried

to run this it would break that's

because I am still trying to make a

reference to this state which does not

exist in this function this is where

hooks will come in

play so let's import a function called

you use estate use state is a function

that returns an array with exactly two

items inside of it the first item is the

value and the second item is a function

that updates that value you can also

pass in an initial value to use state

and I'll show you what I mean by that

I'm going to use destructuring

assignment to pull these two items out

of the array so that I can use them and

now instead of this state and the set

state I will use text and set text and I

pass in button has not been clicked to

the use state function in order to set

the initial value we don't have to pass

in an initial value but I am here

because I want button has not been

clicked to be displayed initially now as

you can see this component works just

like the class version except now we are

using hooks with function components now

let's add a new piece of state let's say

we want to count each time the user

clicks the button well all we have to do

is create more state by using use state

like so then inside of the on click for

the button I'll also call set count and

set it equal to count plus 1 below the

button I'll display the count like this

as you can see the new way of handling

state is a little bit different than the

old way but it's still pretty easy to

understand

in my opinion where it starts to get a

little bit confusing is when you're

trying to replace the lifecycle methods

using hooks and that's because it takes

a bit of a mindset shift instead of

thinking about react components as

having life cycles and then reacting to

certain parts within that cycle we need

to think about reacting to certain

pieces of data change we need to think

whenever some piece of data updates what

do we want to do we need to think about

it like hey when this variable changes

what do we want to do it can be a little

bit confusing at first but in my opinion

it's a much better way to think about

web application programming so let's go

ahead and get into that mindset let's

say that we want to save the number of

times that the user has clicked the

button so that when they refresh the

page or when they come back to this web

page the number of clicks will be saved

we can use local storage to save the

number of clicks but how can we access

local storage and then set the initial

value of count on component mount to do

this we can utilize another hook called

effect start by importing the use effect

function now use effect is a function

that accepts a function as its first

argument and an array as its second

argument there are three scenarios that

I want to talk about in regards to this

second argument if you don't provide any

array at all the function passed in as

the first argument will run every single

time the componentry renders if you pass

in an empty array like this the function

will only run the very first time the

component renders this is effectively

the same as component did mount lastly

if you want to only run the function

when a specific variable changes then

you put the variable into this array and

whenever that variable changes it will

run the function regardless of which of

the three scenarios you use the function

will always run on mouth that's

something to think about for this first

effect we want to only run it unmount so

we'll pass in an empty array what I want

to do when the component mounts is check

local storage for an existing count and

if it exists I want to set the count to

that number but we also need to set the

count in local storage in order for

there to ever be a value there so for

this we can use another effect but this

time we will run it each time the count

changes and what we want to do here is

set the local storage each time we set

the count now each time count is updated

we're gonna run this line of code here

as you can see using hooks is quite a

bit of a different way of thinking about

react components the reality is the new

way is actually more powerful and allows

us to actually write less code like I

said earlier I'm gonna make a video on

more benefits of hooks and also how to

create your own hooks now if you enjoyed

this video please give me a thumbs up

follow me on social media for dev tips

or if you just want to stay updated and

I'll see you all in the next video

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