Vue is a popular front-end JavaScript framework launched by Evan You in 2014. Vue provides a very simple and intuitive way to build user interfaces through the use of directives and components. Vue's slogan is a progressive framework because it can be gradually applied to a project. Although Vue has shown excellent performance, what technology is it built on? This article will explore the underlying development of Vue.

The bottom layer of Vue is mainly built by the following technologies:

1. JavaScript

The bottom layer of Vue is mainly written in JavaScript. JavaScript is an object-oriented programming language, and its application scope continues to expand due to its increasing popularity in front-end development. Vue's core code, including life cycle functions and rendering functions, are written in native JavaScript.

2. Virtual DOM

The bottom layer of Vue uses Virtual DOM technology to improve performance. Virtual DOM refers to a virtual JavaScript object that describes the structure and style of real DOM nodes, but does not actually present it. Vue uses Virtual DOM to quickly perform DOM operations, thus improving performance.

There are two main libraries that implement Virtual DOM. One is React's implementation library warehouse React.js, and the other is Vue's implementation library warehouse Snabbdom.js.

3. VNode

VNode is an important concept in Vue and can be regarded as the description of Virtual DOM node. VNode describes a node's type, attributes, events, subnodes and other information. In Vue, each component generates a VNode tree, which represents the view structure of the component in a specific state. When Vue detects data changes, it regenerates the VNode tree and compares the old and new VNode trees to generate differences and ultimately updates the view.

4. Compiler

The bottom layer of Vue also includes a compiler, which is used to convert templates into rendering functions and generate VNode trees. In Vue, a template is a combination of HTML tags and Vue instructions. The VNode tree is generated by the compiler and finally rendered on the page.

Since the compilation process of Vue takes a long time, Vue provides a pre-compilation option. In the development environment, use components such as Vue.component() or Vue.extend() to register global components, and use template option or render function provides a template, then the vnode render function will be automatically generated at compile time, thereby improving the rendering speed. Template optimization and error checking can also be performed at compile time.

5. MVVM mode

The bottom layer of Vue uses the MVVM mode to implement data binding. MVVM is the abbreviation of Model-View-ViewModel. It is a design pattern often used to decouple data and UI. In Vue, the ViewModel is responsible for managing the communication between the model and the view. When the data changes, it automatically updates the view and vice versa.

6. Dependency tracking

The bottom layer of Vue also implements a dependency tracking mechanism. When the data that the Vue instance depends on changes, it will automatically re-render the corresponding component to update the view. The underlying layer of Vue implements dependency tracking through the Watcher component.

Watcher is an important component of Vue. It automatically collects dependent data when the component is initialized and monitors dependencies through the observe module. When the data changes, the Watcher is notified to recalculate the component and update the changes. to view. At the same time, Watcher also implements an asynchronous queue mechanism to merge multiple Watchers in the same event loop to improve performance.

Summary

The bottom layer of Vue is mainly built by technologies such as JavaScript, Virtual DOM, VNode, compiler, MVVM mode and dependency tracking mechanism. These core technologies of Vue realize Vue's data binding, componentization, progressive and other features, improving development efficiency and user experience. An in-depth understanding of the underlying layers of Vue will help us better understand how Vue works and develop Vue applications more efficiently.

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