Node.js is a JavaScript runtime environment for scalable network applications that uses an event-driven, non-blocking I/O model. Node emitter (Emitter) is an interactive data communication module provided by Node.js. It can implement the observer mode between objects, so that an object can be monitored by multiple users at the same time, and automatically when the object status changes. Notify all users. In this article, we will introduce how to use Node.js's emitter to implement object monitoring and event triggering.
First of all, we need to understand some basic concepts of launchers. Emitter is a built-in module of Node.js that implements event management mechanism. It is an event trigger that provides the functions of registering events, emitting events and removing event listeners. In Node.js, most modules inherit from the EventEmitter class, so they all have an emitter instance that they can use to implement event handling.
Before using the launcher, we need to understand some basic knowledge. First, to create an emitter instance, we need to introduce the events module and create an EventEmitter object. The code is as follows:
const EventEmitter = require('events'); const emitter = new EventEmitter();
Here we use the require
function to introduce the built-in module of Node.js events
, and created an EventEmitter object emitter
for event emission and monitoring.
Then, we need to implement event registration, processing and removal. For event registration and removal, we can use the on
and off
methods, and for event processing, we can use the emit
method. Here are some basic examples:
function callback() { console.log('event is emitted'); } // 注册事件监听器,监听event事件 emitter.on('event', callback); // 触发event事件,会自动调用callback函数 emitter.emit('event'); // 移除event事件监听器,不再监听event事件 emitter.off('event', callback);
In the above example, we used the on
method to register an event listener. When the event 'event'
is emitted, the callback
function is automatically called. Then, we used the emit
method to emit the event 'event'
, which triggered the callback
function. Finally, we use the off
method to remove the callback
function's monitoring of the event 'event'
.
In addition to the on
, off
, and emit
methods, we can also use some other methods to operate the emitter. Among them, the once
method is similar to the on
method. The difference is that the once
method will automatically delete the event listener after the event is emitted once. In addition, the prependListener
method can insert the event listener to the front of the event listener list, and the prependOnceListener
method provides the event listener to the front of the listener list. and will only be called once.
// 在所有事件监听器之前添加事件监听器 emitter.prependListener('event', callback); // 在所有事件监听器之前添加事件监听器,只会调用一次 emitter.prependOnceListener('event', callback);
Of course, we can also use the eventNames
method to get the name list of all events registered on the current object.
const eventNames = emitter.eventNames(); console.log(eventNames); // ['event']
Overall, using Node.js’ emitters is a very useful way to communicate. Emitters allow us to establish loose coupling relationships between objects, reducing application complexity and maintenance costs. Using emitters, we can easily implement data communication and event handling between objects, thereby improving the reliability and scalability of our applications.
The above is the detailed content of How to use nodejs launcher. For more information, please follow other related articles on the PHP Chinese website!

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 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 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.

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 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 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 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.

React components can be defined by functions or classes, encapsulating UI logic and accepting input data through props. 1) Define components: Use functions or classes to return React elements. 2) Rendering component: React calls render method or executes function component. 3) Multiplexing components: pass data through props to build a complex UI. The lifecycle approach of components allows logic to be executed at different stages, improving development efficiency and code maintainability.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

SublimeText3 Chinese version
Chinese version, very easy to use

Atom editor mac version download
The most popular open source editor

VSCode Windows 64-bit Download
A free and powerful IDE editor launched by Microsoft

Zend Studio 13.0.1
Powerful PHP integrated development environment

DVWA
Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software