Home Web Front-end JS Tutorial How to use state and setState in react (detailed tutorial)

How to use state and setState in react (detailed tutorial)

Jun 22, 2018 pm 02:21 PM
react setstate state

This article mainly introduces the use of state and setState in react study notes. The editor thinks it is quite good, so I will share it with you now and give it as a reference. Let’s follow the editor and take a look.

In react, state and setState() are used to control the state of components.

state

state is used in react to store component data status, which can be compared to data in vue.

1. The role of state

state is an object of a component in React. React treats the user interface as a state machine, imagines that it has different states and then renders these State can easily keep the user interface consistent with the data.

In React, updating the state of a component will cause the user interface to be re-rendered (do not operate the DOM). Simply put, the user interface will change with the state And change.

2. How state works

The commonly used method to notify React of data changes is to call setState(data, callback). This method will merge data into this .state, and re-render the component. After rendering is completed, call the optional

callback. In most cases, there is no need to provide a callback, because React will be responsible for updating the interface to the latest state.

setState()

The difference from vue is that state cannot be modified directly and needs to be modified through the setState() method.

1. SetState() will not take effect immediately after updating the component state. In order to improve performance, react will update the state in batches and then render, which is an asynchronous operation. Therefore, it is not necessary to obtain the value of state immediately after setSate(). The status after the update.

2. The first parameter of setState() accepts two types of parameters, Object and Function

Object

1

2

3

this.setState({

 msg: '更新state msg'

})

Copy after login

When the parameter is Object At this time, it can be the key in the corresponding state, and the value is the new value.

Function

When the parameter is a function, setState() will pass the result of the previous setState() as a parameter to this function

1

2

3

4

5

6

7

8

9

10

...

constructor () {

 this.state = { counter: 0 }

}

add() {

 this.setState({ counter: this.state.counter + 1 })

 this.setState({ counter: this.state.counter + 1 }) // 此时`this.state.counter`的值还是初始值0,,所以这个操作是无效的

 this.setState(prevState => { counter: prevState.counter + 1 }) // `prevState.counter` 为上次更新之后的值,即是1

}

...

Copy after login

setState() The second parameter is a callback function, indicating that the state update is completed

1

2

3

4

5

this.setState({

 msg: '更新state msg'

}, () => {

 console.log('state 更新完毕')

})

Copy after login

According to this, you can use Promise and async/await to encapsulate it into a synchronous operation

1

2

3

4

5

6

7

8

9

10

setStateAsync(state) {

 return new Promise(resolve => {

  this.setState(state, resolve)

 })

}

// 使用

async add() {

 await setStateAsync({ counter: this.state.counter + 1 })

 console.log('state 更新完毕')

}

Copy after login

The above is what I compiled Everyone, I hope it will be helpful to everyone in the future.

Related articles:

How to use the swiper component to achieve image switching display in WeChat Mini Program

What are there in vue2.0 Commonly used UI libraries?

How to convert a character into an integer in C

#How to merge vue2.0 and animate.css together (details Tutorial)

The above is the detailed content of How to use state and setState in react (detailed tutorial). For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Roblox: Bubble Gum Simulator Infinity - How To Get And Use Royal Keys
3 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
Nordhold: Fusion System, Explained
3 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

Hot Topics

Java Tutorial
1664
14
PHP Tutorial
1269
29
C# Tutorial
1248
24
How to build a reliable messaging app with React and RabbitMQ How to build a reliable messaging app with React and RabbitMQ Sep 28, 2023 pm 08:24 PM

How to build a reliable messaging application with React and RabbitMQ Introduction: Modern applications need to support reliable messaging to achieve features such as real-time updates and data synchronization. React is a popular JavaScript library for building user interfaces, while RabbitMQ is a reliable messaging middleware. This article will introduce how to combine React and RabbitMQ to build a reliable messaging application, and provide specific code examples. RabbitMQ overview:

React Router User Guide: How to implement front-end routing control React Router User Guide: How to implement front-end routing control Sep 29, 2023 pm 05:45 PM

ReactRouter User Guide: How to Implement Front-End Routing Control With the popularity of single-page applications, front-end routing has become an important part that cannot be ignored. As the most popular routing library in the React ecosystem, ReactRouter provides rich functions and easy-to-use APIs, making the implementation of front-end routing very simple and flexible. This article will introduce how to use ReactRouter and provide some specific code examples. To install ReactRouter first, we need

PHP, Vue and React: How to choose the most suitable front-end framework? PHP, Vue and React: How to choose the most suitable front-end framework? Mar 15, 2024 pm 05:48 PM

PHP, Vue and React: How to choose the most suitable front-end framework? With the continuous development of Internet technology, front-end frameworks play a vital role in Web development. PHP, Vue and React are three representative front-end frameworks, each with its own unique characteristics and advantages. When choosing which front-end framework to use, developers need to make an informed decision based on project needs, team skills, and personal preferences. This article will compare the characteristics and uses of the three front-end frameworks PHP, Vue and React.

Integration of Java framework and front-end React framework Integration of Java framework and front-end React framework Jun 01, 2024 pm 03:16 PM

Integration of Java framework and React framework: Steps: Set up the back-end Java framework. Create project structure. Configure build tools. Create React applications. Write REST API endpoints. Configure the communication mechanism. Practical case (SpringBoot+React): Java code: Define RESTfulAPI controller. React code: Get and display the data returned by the API.

How to use React to develop a responsive backend management system How to use React to develop a responsive backend management system Sep 28, 2023 pm 04:55 PM

How to use React to develop a responsive backend management system. With the rapid development of the Internet, more and more companies and organizations need an efficient, flexible, and easy-to-manage backend management system to handle daily operations. As one of the most popular JavaScript libraries currently, React provides a concise, efficient and maintainable way to build user interfaces. This article will introduce how to use React to develop a responsive backend management system and give specific code examples. Create a React project first

Vue.js vs. React: Project-Specific Considerations Vue.js vs. React: Project-Specific Considerations Apr 09, 2025 am 12:01 AM

Vue.js is suitable for small and medium-sized projects and fast iterations, while React is suitable for large and complex applications. 1) Vue.js is easy to use and is suitable for situations where the team is insufficient or the project scale is small. 2) React has a richer ecosystem and is suitable for projects with high performance and complex functional needs.

React's Role in HTML: Enhancing User Experience React's Role in HTML: Enhancing User Experience Apr 09, 2025 am 12:11 AM

React combines JSX and HTML to improve user experience. 1) JSX embeds HTML to make development more intuitive. 2) The virtual DOM mechanism optimizes performance and reduces DOM operations. 3) Component-based management UI to improve maintainability. 4) State management and event processing enhance interactivity.

What closures does react have? What closures does react have? Oct 27, 2023 pm 03:11 PM

React has closures such as event handling functions, useEffect and useCallback, higher-order components, etc. Detailed introduction: 1. Event handling function closure: In React, when we define an event handling function in a component, the function will form a closure and can access the status and properties within the component scope. In this way, the state and properties of the component can be used in the event processing function to implement interactive logic; 2. Closures in useEffect and useCallback, etc.

See all articles