Learn React Hooks In 6 Minutes
Summary
TLDRThis 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
🚀 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.
🔄 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.
Mindmap
Keywords
💡React
💡Class Components
💡Functional Components
💡React Hooks
💡useState
💡useEffect
💡Lifecycle Methods
💡Local Storage
💡Component Mount
💡State Management
💡Web Application Programming
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
[Music]
تصفح المزيد من مقاطع الفيديو ذات الصلة
Components | Mastering React: An In-Depth Zero to Hero Video Series
React useState() hook introduction 🎣
React Hooks and Their Rules | Lecture 157 | React.JS 🔥
useState Hook | Mastering React: An In-Depth Zero to Hero Video Series
useEffect Hook | Mastering React: An In-Depth Zero to Hero Video Series
What are Custom Hooks When to Create One | Lecture 166 | React.JS 🔥
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