search
HomeWeb Front-endFront-end Q&AWhat does es6 promise mean?

In es6, promise means "commitment". Promise represents the result of an asynchronous operation. It is a new asynchronous programming solution. It is represented as an object in the code and is mainly used to solve the callback area problem. The syntax is "new Promise(function(resolve, reject){..})".

What does es6 promise mean?

The operating environment of this tutorial: Windows 10 system, ECMAScript version 6.0, Dell G3 computer.

What is the meaning of promise in es6

Promise means promise. The core idea behind it is that promise represents the result of an asynchronous operation.

is a new asynchronous programming solution in es6, which is represented as an object in the code.

Promise is a solution provided by js asynchronous programming, mainly used to solve the problem of callback area.

Promise has three states, namely

  • Pending (in progress) initial state

  • Fulfilled (successful) means The operation is successful

  • rejected (failed) means the operation failed

Note: The three states of the Promise object are not affected by the outside world , only events stored in the promise that will end in the future will be affected. That is to say, only the result of asynchronous operation can determine the current state, and no other operation can change this state.

Once the Promise state changes, it is irreversible.

Pending (in progress) state can Transition to the Fulfilled (successful) state

Pending (in progress) state can be transitioned to the rejected (failed) state

promise Only these two situations will change the state. Once these two situations occur If the status changes, then the status is solidified and will always maintain this result.

Basic usage

Syntax:

new Promise( function(resolve, reject) {...} /* executor */  )

Principle:

When building a Promise object, you need to pass in an executor function. The main business processes are executed in the executor function.

The executor function is called immediately when the Promise constructor is executed. The resolve and reject

functions are passed to the executor as parameters. When the resolve and reject

functions are called, respectively The promise's status changes to fulfilled or rejected. Once the state changes, it will not change again, and this result can be obtained at any time.

After calling the resolve function in the executor function, the callback function set by promise.then will be triggered; and after calling the reject

function, the callback function set by promise.catch will be triggered.

As shown in the figure below:

What does es6 promise mean?

The example is as follows:

Create a new Promise object

You need to pass in a callback function. The callback function has 2 parameters, representing resolve (resolve) and reject (reject), and both parameters are functions

If neither parameter is called, the default pending state

let promise=new Promise(function(resolve,reject){
});//pending状态

Call the resolve function, which represents the state of Promise, and will change from pending==>fulfilled

let promise=new Promise(function(resolve,reject){
resolve();
});//fulfilled状态

Call the reject function, which represents the state of Promise, and will change from pending==>rejected

let promise=new Promise(function(resolve,reject){
reject();
});//rejected 状态

【Related recommendations: javascript video tutorial, web front-end

The above is the detailed content of What does es6 promise mean?. For more information, please follow other related articles on the PHP Chinese website!

Statement
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
React Inside HTML: Integrating JavaScript for Dynamic Web PagesReact Inside HTML: Integrating JavaScript for Dynamic Web PagesApr 16, 2025 am 12:06 AM

To integrate React into HTML, follow these steps: 1. Introduce React and ReactDOM in HTML files. 2. Define a React component. 3. Render the component into HTML elements using ReactDOM. Through these steps, static HTML pages can be transformed into dynamic, interactive experiences.

The Benefits of React: Performance, Reusability, and MoreThe Benefits of React: Performance, Reusability, and MoreApr 15, 2025 am 12:05 AM

React’s popularity includes its performance optimization, component reuse and a rich ecosystem. 1. Performance optimization achieves efficient updates through virtual DOM and diffing mechanisms. 2. Component Reuse Reduces duplicate code by reusable components. 3. Rich ecosystem and one-way data flow enhance the development experience.

React: Creating Dynamic and Interactive User InterfacesReact: Creating Dynamic and Interactive User InterfacesApr 14, 2025 am 12:08 AM

React is the tool of choice for building dynamic and interactive user interfaces. 1) Componentization and JSX make UI splitting and reusing simple. 2) State management is implemented through the useState hook to trigger UI updates. 3) The event processing mechanism responds to user interaction and improves user experience.

React vs. Backend Frameworks: A ComparisonReact vs. Backend Frameworks: A ComparisonApr 13, 2025 am 12:06 AM

React is a front-end framework for building user interfaces; a back-end framework is used to build server-side applications. React provides componentized and efficient UI updates, and the backend framework provides a complete backend service solution. When choosing a technology stack, project requirements, team skills, and scalability should be considered.

HTML and React: The Relationship Between Markup and ComponentsHTML and React: The Relationship Between Markup and ComponentsApr 12, 2025 am 12:03 AM

The relationship between HTML and React is the core of front-end development, and they jointly build the user interface of modern web applications. 1) HTML defines the content structure and semantics, and React builds a dynamic interface through componentization. 2) React components use JSX syntax to embed HTML to achieve intelligent rendering. 3) Component life cycle manages HTML rendering and updates dynamically according to state and attributes. 4) Use components to optimize HTML structure and improve maintainability. 5) Performance optimization includes avoiding unnecessary rendering, using key attributes, and keeping the component single responsibility.

React and the Frontend: Building Interactive ExperiencesReact and the Frontend: Building Interactive ExperiencesApr 11, 2025 am 12:02 AM

React is the preferred tool for building interactive front-end experiences. 1) React simplifies UI development through componentization and virtual DOM. 2) Components are divided into function components and class components. Function components are simpler and class components provide more life cycle methods. 3) The working principle of React relies on virtual DOM and reconciliation algorithm to improve performance. 4) State management uses useState or this.state, and life cycle methods such as componentDidMount are used for specific logic. 5) Basic usage includes creating components and managing state, and advanced usage involves custom hooks and performance optimization. 6) Common errors include improper status updates and performance issues, debugging skills include using ReactDevTools and Excellent

React and the Frontend Stack: The Tools and TechnologiesReact and the Frontend Stack: The Tools and TechnologiesApr 10, 2025 am 09:34 AM

React is a JavaScript library for building user interfaces, with its core components and state management. 1) Simplify UI development through componentization and state management. 2) The working principle includes reconciliation and rendering, and optimization can be implemented through React.memo and useMemo. 3) The basic usage is to create and render components, and the advanced usage includes using Hooks and ContextAPI. 4) Common errors such as improper status update, you can use ReactDevTools to debug. 5) Performance optimization includes using React.memo, virtualization lists and CodeSplitting, and keeping code readable and maintainable is best practice.

React's Role in HTML: Enhancing User ExperienceReact's Role in HTML: Enhancing User ExperienceApr 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.

See all articles

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

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
4 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. Best Graphic Settings
4 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. How to Fix Audio if You Can't Hear Anyone
4 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. Chat Commands and How to Use Them
4 weeks agoBy尊渡假赌尊渡假赌尊渡假赌

Hot Tools

SAP NetWeaver Server Adapter for Eclipse

SAP NetWeaver Server Adapter for Eclipse

Integrate Eclipse with SAP NetWeaver application server.

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

EditPlus Chinese cracked version

EditPlus Chinese cracked version

Small size, syntax highlighting, does not support code prompt function

MinGW - Minimalist GNU for Windows

MinGW - Minimalist GNU for Windows

This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.