The stages of nodejs event loop: 1. timers (timer) stage; 2. pending callbacks stage; 3. idle, prepare stage; 4. poll (polling) stage; 5. check (check) stage ;6. Close callbacks stage.

The operating environment of this tutorial: windows7 system, nodejs version 12.19.0, DELL G3 computer.
nodejs event loop
When Node.js starts, the event loop will be initialized. Each event loop will contain six cycle stages, nodejs time loop and browser The events were completely different.

Note: Each box in the figure is called a phase of the practice cycle, and these six phases are an event cycle.
Stage summary
- ##timers (timers): This stage executes those specified by setTimeout () and setInterval() dispatched callback functions.
- pending callbacks (I/O callbacks): This stage will execute almost all callback functions, except close callbacks(close callbacks) and those specified by timers and setImmediate() scheduled callbacks.
setImmediate is approximately equal to setTimeout(callback, 0) - idle (idle), prepare: This stage is only used internally.
- poll (polling): Retrieve new I/O events; Node will block at this stage when appropriate.
- check (check): The callback set by setImmediate() will be called at this stage.
- close callbacks (callbacks for closing events): Callbacks such as socket.on(‘close’,…) are called at this stage.
- If the poll queue is not empty, the event loop will execute the queue synchronously until the queue is empty or the executed callback reaches the system upper limit;
- If the poll queue is empty, the following will happen:
- - If the code has been set with a callback by setImmediate() , the event loop will enter the result poll phase into the check phase, and execute the queue in the check phase (the queue in the check phase is set by setImmediate).
- If the code does not set setImmediate(callback), the event loop will block at this stage and wait for the callback to join the poll queue, and execute it immediately once it arrives.
- If the poll queue enters the empty state (that is, the poll phase is idle), the event The loop will check timers. If one or more timers have arrived, the event loop will enter the timer phase in loop order and execute the timer queue.
nodejs tutorial"]
The above is the detailed content of What are the stages of the nodejs event loop?. For more information, please follow other related articles on the PHP Chinese website!
React: The Power of a JavaScript Library for Web DevelopmentApr 18, 2025 am 12:25 AMReact is a JavaScript library developed by Meta for building user interfaces, with its core being component development and virtual DOM technology. 1. Component and state management: React manages state through components (functions or classes) and Hooks (such as useState), improving code reusability and maintenance. 2. Virtual DOM and performance optimization: Through virtual DOM, React efficiently updates the real DOM to improve performance. 3. Life cycle and Hooks: Hooks (such as useEffect) allow function components to manage life cycles and perform side-effect operations. 4. Usage example: From basic HelloWorld components to advanced global state management (useContext and
React's Ecosystem: Libraries, Tools, and Best PracticesApr 18, 2025 am 12:23 AMThe React ecosystem includes state management libraries (such as Redux), routing libraries (such as ReactRouter), UI component libraries (such as Material-UI), testing tools (such as Jest), and building tools (such as Webpack). These tools work together to help developers develop and maintain applications efficiently, improve code quality and development efficiency.
React and Frontend Development: A Comprehensive OverviewApr 18, 2025 am 12:23 AMReact is a JavaScript library developed by Facebook for building user interfaces. 1. It adopts componentized and virtual DOM technology to improve the efficiency and performance of UI development. 2. The core concepts of React include componentization, state management (such as useState and useEffect) and the working principle of virtual DOM. 3. In practical applications, React supports from basic component rendering to advanced asynchronous data processing. 4. Common errors such as forgetting to add key attributes or incorrect status updates can be debugged through ReactDevTools and logs. 5. Performance optimization and best practices include using React.memo, code segmentation and keeping code readable and maintaining dependability
The Power of React in HTML: Modern Web DevelopmentApr 18, 2025 am 12:22 AMThe application of React in HTML improves the efficiency and flexibility of web development through componentization and virtual DOM. 1) React componentization idea breaks down the UI into reusable units to simplify management. 2) Virtual DOM optimization performance, minimize DOM operations through diffing algorithm. 3) JSX syntax allows writing HTML in JavaScript to improve development efficiency. 4) Use the useState hook to manage state and realize dynamic content updates. 5) Optimization strategies include using React.memo and useCallback to reduce unnecessary rendering.
Understanding React's Primary Function: The Frontend PerspectiveApr 18, 2025 am 12:15 AMReact's main functions include componentized thinking, state management and virtual DOM. 1) The idea of componentization allows splitting the UI into reusable parts to improve code readability and maintainability. 2) State management manages dynamic data through state and props, and changes trigger UI updates. 3) Virtual DOM optimization performance, update the UI through the calculation of the minimum operation of DOM replica in memory.
Frontend Development with React: Advantages and TechniquesApr 17, 2025 am 12:25 AMThe advantages of React are its flexibility and efficiency, which are reflected in: 1) Component-based design improves code reusability; 2) Virtual DOM technology optimizes performance, especially when handling large amounts of data updates; 3) The rich ecosystem provides a large number of third-party libraries and tools. By understanding how React works and uses examples, you can master its core concepts and best practices to build an efficient, maintainable user interface.
React vs. Other Frameworks: Comparing and Contrasting OptionsApr 17, 2025 am 12:23 AMReact is a JavaScript library for building user interfaces, suitable for large and complex applications. 1. The core of React is componentization and virtual DOM, which improves UI rendering performance. 2. Compared with Vue, React is more flexible but has a steep learning curve, which is suitable for large projects. 3. Compared with Angular, React is lighter, dependent on the community ecology, and suitable for projects that require flexibility.
Demystifying React in HTML: How It All WorksApr 17, 2025 am 12:21 AMReact operates in HTML via virtual DOM. 1) React uses JSX syntax to write HTML-like structures. 2) Virtual DOM management UI update, efficient rendering through Diffing algorithm. 3) Use ReactDOM.render() to render the component to the real DOM. 4) Optimization and best practices include using React.memo and component splitting to improve performance and 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

WebStorm Mac version
Useful JavaScript development tools

Atom editor mac version download
The most popular open source editor

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

SublimeText3 English version
Recommended: Win version, supports code prompts!

SublimeText3 Mac version
God-level code editing software (SublimeText3)







