This article will help you learn Vue and gain an in-depth understanding of the responsiveness principles in Vue. I hope it will be helpful to you!
This article commemorates the passing of responsive syntax sugar
Without further ado, let’s get straight to the point. Responsiveness is Applications in daily development are very common. Here is a simple example:
let a=3 let b=a*10 console.log(b)//30 a=4 console.log(b)//40
At this time we want b=4*10, which is obviously not possible, even if we add a ## in front #var will only
variable promotion, the value we give will not be promoted.
import { reactive } from 'vue' let state = reactive({ a: 3 }) let b = computed(() => state.a * 10) console.log(b.value) // 30 state.a = 4 console.log(b.value) // 40Only a simple
responsive API can achieve the effect of tracking changes. [Related recommendations:
vuejs video tutorial, web front-end development]
Analyze reactive
In fact, Vue3reactive is essentially a
publish-subscribe model
reactive system will automatically trigger an update of the view. This is because it tracks data changes in the dependency graph and achieves this by associating it with updates to the view
class Dep{ constructor(value){ this.subscribers=new Set() this._value=value } get value(){ this.depend() return this._value } set value(newValue){ this._value=newValue this.notify() } depend(){ if(activeEffect){ this.subscribers.add(activeEffect) } } notify(){ this.subscribers.forEach(effect=>{ effect() }) } }Let’s analyze this code:
When the value of the variable changes, it can automatically notify all subscribers to updateDefine a
- subscribe
attribute as a subscriber list to store all Subscriber information
- depend
function is used to manage dependency relationships, that is, the variable
- notify
function on which the subscriber depends is used as a notification The value of this variable has changed for all subscribers
Vue2’s Object.defineProperty
In fact, in the Vue2 period, responsiveness was implemented byObject.defineProperty, but in Vue3 it was switched to
Proxy, let’s wait and see the reason combined with the actual code; let’s first take a look at how Vue2 is implemented:
function reactive(raw){ Object.keys(raw).forEach(ket=>{ const dep=new Dep() let value=raw[key] Object.definProperty(raw,key,{ get(){ dep.depend() return value }, //当属性发生 set(newValue){ value=newValue dep.notify() } }) }) //这时候返回的原始对象已经具有响应性 return raw }Such a simple reactive API is implemented
But the shortcomings here are obvious:
In Vue 2.x, the object passed in will be directly changed by Vue.observable But in Vue3, it is Will return a responsive proxy, but directly changing the source object is still unresponsive
Of course, this is a historical limitation. At that time, ES5 could only chooseWhen When we
- add or delete
Unable to detect thethe properties of the object, Vue2's responsiveness cannot be detected. Since Vue will perform getter/setter conversion on the property when initializing the instance, the property must be in
dataOnly when it exists on the object can Vue convert it into a responsive
- subscript and length changes of the array
Object.definProperty, but in the ES6 version, there are more
Proxy. At this time, Vue’s response The formula has been upgraded
Vue3’s Proxy
Vue3 usesProxy to monitor data changes. Compared with Vue2, it not only solves In addition to the above problems, there are also these advantages:
Let's take a look at what the actual code looks like:No need to use
- vue.$set
Comprehensive array change detection, eliminating invalid boundary conditions in Vue2to trigger reactivity, which makes the code look more
Introduction- Reduces the amount of responsive code written in Vue3, which makes our development more convenient
const reactiveHandles={ get(target,key,receiver){ const dep=getDep(target,key) dep.depend() return Reflect.get(target,key,receiver) }, set(target,key,value,receiver){ const dep=getDep(target,key) const result=Reflect.set(target,key,value,receiver) dep.notify() return result } }The responsive way is to
collect dependencies on objects. The essence of Vue3 responsiveness
ref
There is a sentence in the official documentation: The various limitations ofreactive() are ultimately because JavaScript cannot function The "reference" mechanism for all value types, and the limitation of reactive is:
And this time it is neededcan only handle observable data structures, such as arrays and objects; and unobservable data structures , such as primitive data types, they cannot be monitored
- Can only process data defined in the component where it is located, and cannot process global variables
ref is here, ref was born for
basic data type, which makes up for the shortcomings of reactive. To put it simply, ref is more suitable for simple single variable values (but in actual development Most of the time it’s just refs. Hahahaha
(Learning video sharing: vuejs introductory tutorial, Basic programming video)
The above is the detailed content of An article explaining the principle of reactivity in Vue in detail. For more information, please follow other related articles on the PHP Chinese website!

JavaScript 不提供任何内存管理操作。相反,内存由 JavaScript VM 通过内存回收过程管理,该过程称为垃圾收集。

vscode自身是支持vue文件组件跳转到定义的,但是支持的力度是非常弱的。我们在vue-cli的配置的下,可以写很多灵活的用法,这样可以提升我们的生产效率。但是正是这些灵活的写法,导致了vscode自身提供的功能无法支持跳转到文件定义。为了兼容这些灵活的写法,提高工作效率,所以写了一个vscode支持vue文件跳转到定义的插件。

Node 19已正式发布,下面本篇文章就来带大家详解了解一下Node.js 19的 6 大特性,希望对大家有所帮助!

选择一个Node的Docker镜像看起来像是一件小事,但是镜像的大小和潜在漏洞可能会对你的CI/CD流程和安全造成重大的影响。那我们如何选择一个最好Node.js Docker镜像呢?

本篇文章给大家整理和分享几个前端文件处理相关的实用工具库,共分成6大类一一介绍给大家,希望对大家有所帮助。


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

SAP NetWeaver Server Adapter for Eclipse
Integrate Eclipse with SAP NetWeaver application server.

EditPlus Chinese cracked version
Small size, syntax highlighting, does not support code prompt function

Dreamweaver Mac version
Visual web development tools

Notepad++7.3.1
Easy-to-use and free code editor

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