What does Javascript macro task include?

Javascript is a programming language widely used in web development, and macro tasks are an important concept in the Javascript event loop. It refers to the tasks that need to be executed before the next event loop starts after the current code is executed. In this article, we’ll take a deep dive into what Javascript macro tasks include.

Before understanding the macro tasks of Javascript, we need to first understand the event loop of Javascript. The event loop is a mechanism in Javascript used to execute code and handle events. When Javascript code is executed, it is divided into two types of tasks: macro tasks and micro tasks. The microtask will be cleared before the macrotask is executed, and the macrotask will be suspended in the event loop and executed at the beginning of the next event loop.

So, what does the macro task in Javascript include? The following is their detailed introduction:

1. Rendering

Web page rendering is a very important step in web development. When a page is loaded, the browser parses and converts HTML, CSS, Javascript and other files into visual web pages. In this process, rendering can be considered a macro task. It will be executed after the Javascript is executed but before the next event loop.

2. User interaction

User interaction is a very important event type. In Javascript, user interaction includes clicking, scrolling, dragging and other behaviors. When the user performs an operation, the browser will add these events to the macro task queue so that they can be executed in the next event loop.

3. Timer

Timer is a very commonly used function in Javascript. A timer can execute a piece of code after a specified interval. In Javascript, a timer task is also a macro task and will be executed in the next event loop.

4. Network Request

Network request is another very important function in Javascript. In web pages, we can use Ajax or fetch to make network requests. When the network request returns data, the browser will add these events to the macro task queue and be executed in the next event loop.

5. Resource loading

In web development, we usually add some pictures, videos and other resources to the page. When these resources need to be loaded, the browser will add these tasks to the macro task queue and be executed in the next event loop.

Summary

In Javascript, macro tasks are a very important concept. Macro tasks will be executed before the next event loop starts. They include rendering, user interaction, timers, network requests, resource loading, etc. For example, when a user scrolls a web page, the browser adds the scroll event to the macro task queue and executes it in the next event loop. Understanding the content and execution order of these macro tasks can help us better understand the Javascript event loop mechanism and better control the event flow when writing Javascript code.

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