22 lines
62 KiB
HTML
22 lines
62 KiB
HTML
<!doctype html>
|
||
<html lang="en" dir="ltr" class="docs-wrapper docs-doc-page docs-version-current plugin-docs plugin-id-default docs-doc-id-book1/frame-vue-data-binding">
|
||
<head>
|
||
<meta charset="UTF-8">
|
||
<meta name="generator" content="Docusaurus v2.3.1">
|
||
<title data-rh="true">Vue 的数据绑定机制 | HZFE - 剑指前端 Offer</title><meta data-rh="true" name="viewport" content="width=device-width,initial-scale=1"><meta data-rh="true" name="twitter:card" content="summary_large_image"><meta data-rh="true" property="og:url" content="https://febook.hzfe.org/awesome-interview/book1/frame-vue-data-binding"><meta data-rh="true" name="docusaurus_locale" content="en"><meta data-rh="true" name="docsearch:language" content="en"><meta data-rh="true" name="docusaurus_version" content="current"><meta data-rh="true" name="docusaurus_tag" content="docs-default-current"><meta data-rh="true" name="docsearch:version" content="current"><meta data-rh="true" name="docsearch:docusaurus_tag" content="docs-default-current"><meta data-rh="true" property="og:title" content="Vue 的数据绑定机制 | HZFE - 剑指前端 Offer"><meta data-rh="true" name="description" content="相关问题"><meta data-rh="true" property="og:description" content="相关问题"><link data-rh="true" rel="icon" href="/awesome-interview/img/favicon.ico"><link data-rh="true" rel="canonical" href="https://febook.hzfe.org/awesome-interview/book1/frame-vue-data-binding"><link data-rh="true" rel="alternate" href="https://febook.hzfe.org/awesome-interview/book1/frame-vue-data-binding" hreflang="en"><link data-rh="true" rel="alternate" href="https://febook.hzfe.org/awesome-interview/book1/frame-vue-data-binding" hreflang="x-default"><link data-rh="true" rel="preconnect" href="https://PED5MQGL7T-dsn.algolia.net" crossorigin="anonymous"><link rel="search" type="application/opensearchdescription+xml" title="HZFE - 剑指前端 Offer" href="/awesome-interview/opensearch.xml">
|
||
<link rel="apple-touch-icon" href="/awesome-interview/img/badge.png">
|
||
<link rel="manifest" href="/awesome-interview/manifest.json">
|
||
<link rel="preconnect" href="https://hm.baidu.com">
|
||
<script>var _hmt=_hmt||[];!function(){var e=document.createElement("script");e.src="https://hm.baidu.com/hm.js?c7cd0fd77ac518cc6ef46461cdc9524b";var c=document.getElementsByTagName("script")[0];c.parentNode.insertBefore(e,c)}()</script>
|
||
<script src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js" async data-ad-client="ca-pub-9889934432771967"></script>
|
||
<script src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js?client=ca-pub-9889934432771967" async crossorigin="anonymous"></script><link rel="stylesheet" href="/awesome-interview/assets/css/styles.0f62048e.css">
|
||
<link rel="preload" href="/awesome-interview/assets/js/runtime~main.a75952d5.js" as="script">
|
||
<link rel="preload" href="/awesome-interview/assets/js/main.a5e14537.js" as="script">
|
||
</head>
|
||
<body class="navigation-with-keyboard">
|
||
<script>!function(){function t(t){document.documentElement.setAttribute("data-theme",t)}var e=function(){var t=null;try{t=localStorage.getItem("theme")}catch(t){}return t}();t(null!==e?e:"light")}()</script><div id="__docusaurus">
|
||
<div role="region" aria-label="Skip to main content"><a class="skipToContent_fXgn" href="#docusaurus_skipToContent_fallback">Skip to main content</a></div><nav aria-label="Main" class="navbar navbar--fixed-top navbarHideable_m1mJ"><div class="navbar__inner"><div class="navbar__items"><button aria-label="Toggle navigation bar" aria-expanded="false" class="navbar__toggle clean-btn" type="button"><svg width="30" height="30" viewBox="0 0 30 30" aria-hidden="true"><path stroke="currentColor" stroke-linecap="round" stroke-miterlimit="10" stroke-width="2" d="M4 7h22M4 15h22M4 23h22"></path></svg></button><a class="navbar__brand" href="/awesome-interview/"><div class="navbar__logo"><img src="/awesome-interview/img/badge.svg" alt="HZFE" class="themedImage_ToTc themedImage--light_HNdA"><img src="/awesome-interview/img/badge.svg" alt="HZFE" class="themedImage_ToTc themedImage--dark_i4oU"></div><b class="navbar__title text--truncate">剑指前端 Offer</b></a></div><div class="navbar__items navbar__items--right"><a href="https://github.com/hzfe/awesome-interview" target="_blank" rel="noopener noreferrer" class="navbar__item navbar__link">GitHub<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a><div class="searchBox_ZlJk"><button type="button" class="DocSearch DocSearch-Button" aria-label="Search"><span class="DocSearch-Button-Container"><svg width="20" height="20" class="DocSearch-Search-Icon" viewBox="0 0 20 20"><path d="M14.386 14.386l4.0877 4.0877-4.0877-4.0877c-2.9418 2.9419-7.7115 2.9419-10.6533 0-2.9419-2.9418-2.9419-7.7115 0-10.6533 2.9418-2.9419 7.7115-2.9419 10.6533 0 2.9419 2.9418 2.9419 7.7115 0 10.6533z" stroke="currentColor" fill="none" fill-rule="evenodd" stroke-linecap="round" stroke-linejoin="round"></path></svg><span class="DocSearch-Button-Placeholder">Search</span></span><span class="DocSearch-Button-Keys"></span></button></div></div></div><div role="presentation" class="navbar-sidebar__backdrop"></div></nav><div id="docusaurus_skipToContent_fallback" class="main-wrapper mainWrapper_z2l0 docsWrapper_BCFX"><button aria-label="Scroll back to top" class="clean-btn theme-back-to-top-button backToTopButton_sjWU" type="button"></button><div class="docPage__5DB"><aside class="theme-doc-sidebar-container docSidebarContainer_b6E3"><div class="sidebarViewport_Xe31"><div class="sidebar_njMd sidebarWithHideableNavbar_wUlq"><a tabindex="-1" class="sidebarLogo_isFc" href="/awesome-interview/"><img src="/awesome-interview/img/badge.svg" alt="HZFE" class="themedImage_ToTc themedImage--light_HNdA"><img src="/awesome-interview/img/badge.svg" alt="HZFE" class="themedImage_ToTc themedImage--dark_i4oU"><b>剑指前端 Offer</b></a><nav aria-label="Docs sidebar" class="menu thin-scrollbar menu_SIkG"><ul class="theme-doc-sidebar-menu menu__list"><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-1 menu__list-item"><a class="menu__link" href="/awesome-interview/about">关于我们</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-1 menu__list-item"><a class="menu__link" href="/awesome-interview/">前言</a></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret menu__link--active" aria-expanded="true" href="/awesome-interview/book1/browser-cross-origin">模拟题一</a></div><ul style="display:block;overflow:visible;height:auto" class="menu__list"><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item"><a class="menu__link" tabindex="0" href="/awesome-interview/book1/browser-cross-origin">浏览器：浏览器跨域</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item"><a class="menu__link" tabindex="0" href="/awesome-interview/book1/browser-repain-reflow">浏览器：浏览器的重排重绘</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item"><a class="menu__link" tabindex="0" href="/awesome-interview/book1/engineer-webpack-workflow">工程化：webpack 工作流程</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item"><a class="menu__link menu__link--active" aria-current="page" tabindex="0" href="/awesome-interview/book1/frame-vue-data-binding">框架：Vue 的数据绑定机制</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item"><a class="menu__link" tabindex="0" href="/awesome-interview/book1/frame-vue-computed-watch">框架：Vue 的 computed 和 watch 的区别</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item"><a class="menu__link" tabindex="0" href="/awesome-interview/book1/js-closures">基础：闭包的作用和原理</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item"><a class="menu__link" tabindex="0" href="/awesome-interview/book1/js-module-specs">基础：前端模块化规范</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item"><a class="menu__link" tabindex="0" href="/awesome-interview/book1/css-bfc">样式：BFC 的形成和作用</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item"><a class="menu__link" tabindex="0" href="/awesome-interview/book1/network-security">网络：前端安全</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item"><a class="menu__link" tabindex="0" href="/awesome-interview/book1/coding-promise">编码：实现一个符合 Promises/A+ 规范的 Promise</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item"><a class="menu__link" tabindex="0" href="/awesome-interview/book1/algorithm-balanced-binary-trees">算法：平衡二叉树</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item"><a class="menu__link" tabindex="0" href="/awesome-interview/book1/topic-enter-url-display-xx">综合：浏览器从输入网址到页面展现的过程</a></li></ul></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="/awesome-interview/book2/browser-render-mechanism">模拟题二</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="/awesome-interview/book3/browser-event-loop">模拟题三</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="/awesome-interview/book4/browser-router">模拟题四</a></div></li></ul></nav><button type="button" title="Collapse sidebar" aria-label="Collapse sidebar" class="button button--secondary button--outline collapseSidebarButton_PEFL"><svg width="20" height="20" aria-hidden="true" class="collapseSidebarButtonIcon_kv0_"><g fill="#7a7a7a"><path d="M9.992 10.023c0 .2-.062.399-.172.547l-4.996 7.492a.982.982 0 01-.828.454H1c-.55 0-1-.453-1-1 0-.2.059-.403.168-.551l4.629-6.942L.168 3.078A.939.939 0 010 2.528c0-.548.45-.997 1-.997h2.996c.352 0 .649.18.828.45L9.82 9.472c.11.148.172.347.172.55zm0 0"></path><path d="M19.98 10.023c0 .2-.058.399-.168.547l-4.996 7.492a.987.987 0 01-.828.454h-3c-.547 0-.996-.453-.996-1 0-.2.059-.403.168-.551l4.625-6.942-4.625-6.945a.939.939 0 01-.168-.55 1 1 0 01.996-.997h3c.348 0 .649.18.828.45l4.996 7.492c.11.148.168.347.168.55zm0 0"></path></g></svg></button></div></div></aside><main class="docMainContainer_gTbr"><div class="container padding-top--md padding-bottom--lg"><div class="row"><div class="col docItemCol_VOVn"><div class="docItemContainer_Djhp"><article><nav class="theme-doc-breadcrumbs breadcrumbsContainer_Z_bl" aria-label="Breadcrumbs"><ul class="breadcrumbs" itemscope="" itemtype="https://schema.org/BreadcrumbList"><li class="breadcrumbs__item"><a aria-label="Home page" class="breadcrumbs__link" href="/awesome-interview/"><svg viewBox="0 0 24 24" class="breadcrumbHomeIcon_YNFT"><path d="M10 19v-5h4v5c0 .55.45 1 1 1h3c.55 0 1-.45 1-1v-7h1.7c.46 0 .68-.57.33-.87L12.67 3.6c-.38-.34-.96-.34-1.34 0l-8.36 7.53c-.34.3-.13.87.33.87H5v7c0 .55.45 1 1 1h3c.55 0 1-.45 1-1z" fill="currentColor"></path></svg></a></li><li class="breadcrumbs__item"><span class="breadcrumbs__link">模拟题一</span><meta itemprop="position" content="1"></li><li itemscope="" itemprop="itemListElement" itemtype="https://schema.org/ListItem" class="breadcrumbs__item breadcrumbs__item--active"><span class="breadcrumbs__link" itemprop="name">框架：Vue 的数据绑定机制</span><meta itemprop="position" content="2"></li></ul></nav><div class="tocCollapsible_ETCw theme-doc-toc-mobile tocMobile_ITEo"><button type="button" class="clean-btn tocCollapsibleButton_TO0P">On this page</button></div><div class="theme-doc-markdown markdown"><h1>Vue 的数据绑定机制</h1><h2 class="anchor anchorWithHideOnScrollNavbar_WYt5" id="相关问题">相关问题<a href="#相关问题" class="hash-link" aria-label="Direct link to 相关问题" title="Direct link to 相关问题"></a></h2><ul><li>Vue 是如何实现数据劫持的</li><li>Vue 是如何实现双向绑定的</li><li>MVVM 是什么</li></ul><h2 class="anchor anchorWithHideOnScrollNavbar_WYt5" id="回答关键点">回答关键点<a href="#回答关键点" class="hash-link" aria-label="Direct link to 回答关键点" title="Direct link to 回答关键点"></a></h2><p><code>响应式对象</code> <code>数据劫持</code> <code>双向绑定</code> <code>MVVM（Model-View-ViewModel）</code> <code>发布/订阅模式（publish-subscribe pattern）</code></p><p><strong>响应式对象</strong></p><p>Vue2 通过 <code>Object.defineProperty</code>，Vue3 通过 Proxy 来劫持 state 中各个属性的 setter、getter，通过 getter 收集依赖。当 state 中的数据发生变动之后发布通知给订阅者更新数据。</p><p><strong>双向绑定</strong></p><p>Vue 通过 <code>v-model</code> 实现双向绑定。<code>v-model</code> 实际是 <code>v-bind:xxx</code> 和 <code>v-on:xxx</code> 的语法糖。当触发元素对应的事件（如 input、change 等）时更新数据（ViewModel），当数据（ViewModel）更新时同步更新到元素的对应属性（View）上。</p><p><strong>MVVM（Model-View-ViewModel）</strong></p><p>MVVM 模式是一种软件架构模式，相比 MVC 模式多了一个 ViewModel 层。有助于将图形用户界面的开发与业务逻辑或后端逻辑（数据模型）的开发分离开来。</p><ul><li>Model：模型层，负责处理业务逻辑以及和服务器端进行交互。</li><li>View：视图层，将数据通过 UI 展现出来。</li><li>ViewModel：视图模型层，连接 Model 层和 View 层。</li></ul><h2 class="anchor anchorWithHideOnScrollNavbar_WYt5" id="知识点深入">知识点深入<a href="#知识点深入" class="hash-link" aria-label="Direct link to 知识点深入" title="Direct link to 知识点深入"></a></h2><h3 class="anchor anchorWithHideOnScrollNavbar_WYt5" id="1-前置概念">1. 前置概念<a href="#1-前置概念" class="hash-link" aria-label="Direct link to 1. 前置概念" title="Direct link to 1. 前置概念"></a></h3><p>在详细说明原理之前，需要对以下概念有一定的认知：</p><ol><li>Dep：实现发布订阅模式的模块。</li><li>Watcher：订阅更新和触发视图更新的模块。</li></ol><h3 class="anchor anchorWithHideOnScrollNavbar_WYt5" id="2-实现原理">2. 实现原理<a href="#2-实现原理" class="hash-link" aria-label="Direct link to 2. 实现原理" title="Direct link to 2. 实现原理"></a></h3><p><img loading="lazy" src="https://user-images.githubusercontent.com/3984824/132991936-828bba61-2c87-4ee2-acf0-ffef294760fb.png" alt="image" class="img_ev3q"></p><p>上图是 Vue 官网描述 Vue 内数据变化与发布更新的流程，我们以响应式对象、依赖收集、数据更新的顺序详细说明整个过程。</p><h4 class="anchor anchorWithHideOnScrollNavbar_WYt5" id="21-响应式对象">2.1 响应式对象<a href="#21-响应式对象" class="hash-link" aria-label="Direct link to 2.1 响应式对象" title="Direct link to 2.1 响应式对象"></a></h4><p>Vue2 通过 <code>Object.defineProperty</code>，Vue3 通过 Proxy 来劫持 state 中各个属性的 getter、setter。其中 getter 中主要是通过 Dep 收集依赖这个属性的订阅者，setter 中则是在属性变化后通知 Dep 收集到的订阅者，派发更新。</p><p>以下是 Dep 的伪代码：</p><div class="language-typescript codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#393A34;--prism-background-color:#f6f8fa"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-typescript codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#393A34"><span class="token keyword" style="color:#00009f">export</span><span class="token plain"> </span><span class="token keyword" style="color:#00009f">default</span><span class="token plain"> </span><span class="token keyword" style="color:#00009f">class</span><span class="token plain"> </span><span class="token class-name">Dep</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">static</span><span class="token plain"> target</span><span class="token operator" style="color:#393A34">?</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> Watcher</span><span class="token punctuation" style="color:#393A34">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> subs</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> </span><span class="token builtin">Array</span><span class="token operator" style="color:#393A34"><</span><span class="token plain">Watcher</span><span class="token operator" style="color:#393A34">></span><span class="token punctuation" style="color:#393A34">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token function" style="color:#d73a49">constructor</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">this</span><span class="token punctuation" style="color:#393A34">.</span><span class="token plain">subs </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">[</span><span class="token punctuation" style="color:#393A34">]</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">}</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">/**</span><br></span><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic"> * 添加订阅者（watcher）</span><br></span><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic"> **/</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token function" style="color:#d73a49">addSub</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token plain">sub</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> Watcher</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">this</span><span class="token punctuation" style="color:#393A34">.</span><span class="token plain">subs</span><span class="token punctuation" style="color:#393A34">.</span><span class="token function" style="color:#d73a49">push</span><span class="token punctuation" style="color:#393A34">(</span><span class="token plain">sub</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">}</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">/**</span><br></span><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic"> * 移除订阅者（watcher）</span><br></span><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic"> **/</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token function" style="color:#d73a49">removeSub</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token plain">sub</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> Watcher</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token function" style="color:#d73a49">remove</span><span class="token punctuation" style="color:#393A34">(</span><span class="token keyword" style="color:#00009f">this</span><span class="token punctuation" style="color:#393A34">.</span><span class="token plain">subs</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"> sub</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">}</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">/**</span><br></span><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic"> * 添加订阅（调用订阅者上的 addDep 方法）</span><br></span><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic"> **/</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token function" style="color:#d73a49">depend</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">if</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token plain">Dep</span><span class="token punctuation" style="color:#393A34">.</span><span class="token plain">target</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> Dep</span><span class="token punctuation" style="color:#393A34">.</span><span class="token plain">target</span><span class="token punctuation" style="color:#393A34">.</span><span class="token function" style="color:#d73a49">addDep</span><span class="token punctuation" style="color:#393A34">(</span><span class="token keyword" style="color:#00009f">this</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">}</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">}</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">/**</span><br></span><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic"> * 遍历通知订阅者更新</span><br></span><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic"> **/</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token function" style="color:#d73a49">notify</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">const</span><span class="token plain"> subs </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> </span><span class="token keyword" style="color:#00009f">this</span><span class="token punctuation" style="color:#393A34">.</span><span class="token plain">subs</span><span class="token punctuation" style="color:#393A34">.</span><span class="token function" style="color:#d73a49">slice</span><span class="token punctuation" style="color:#393A34">(</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">for</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token keyword" style="color:#00009f">let</span><span class="token plain"> i </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> </span><span class="token number" style="color:#36acaa">0</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"> l </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> subs</span><span class="token punctuation" style="color:#393A34">.</span><span class="token plain">length</span><span class="token punctuation" style="color:#393A34">;</span><span class="token plain"> i </span><span class="token operator" style="color:#393A34"><</span><span class="token plain"> l</span><span class="token punctuation" style="color:#393A34">;</span><span class="token plain"> i</span><span class="token operator" style="color:#393A34">++</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> subs</span><span class="token punctuation" style="color:#393A34">[</span><span class="token plain">i</span><span class="token punctuation" style="color:#393A34">]</span><span class="token punctuation" style="color:#393A34">.</span><span class="token function" style="color:#d73a49">update</span><span class="token punctuation" style="color:#393A34">(</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">}</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">}</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token punctuation" style="color:#393A34">}</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">Dep</span><span class="token punctuation" style="color:#393A34">.</span><span class="token plain">target </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> </span><span class="token keyword" style="color:#00009f">null</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>以下是生成响应式对象的伪代码：</p><div class="language-typescript codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#393A34;--prism-background-color:#f6f8fa"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-typescript codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic">/**</span><br></span><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic"> * 生成响应式对象</span><br></span><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic"> * 为了方便理解，以下代码略有修改，省略了部分不相关内容</span><br></span><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic"> */</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token keyword" style="color:#00009f">export</span><span class="token plain"> </span><span class="token keyword" style="color:#00009f">function</span><span class="token plain"> </span><span class="token function" style="color:#d73a49">defineReactive</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> obj</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> Object</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> key</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> </span><span class="token builtin">string</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> val</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> </span><span class="token builtin">any</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">const</span><span class="token plain"> dep </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> </span><span class="token keyword" style="color:#00009f">new</span><span class="token plain"> </span><span class="token class-name">Dep</span><span class="token punctuation" style="color:#393A34">(</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> Object</span><span class="token punctuation" style="color:#393A34">.</span><span class="token function" style="color:#d73a49">defineProperty</span><span class="token punctuation" style="color:#393A34">(</span><span class="token plain">obj</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"> key</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> enumerable</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> </span><span class="token boolean" style="color:#36acaa">true</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> configurable</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> </span><span class="token boolean" style="color:#36acaa">true</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token function-variable function" style="color:#d73a49">get</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> </span><span class="token keyword" style="color:#00009f">function</span><span class="token plain"> </span><span class="token function" style="color:#d73a49">reactiveGetter</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">// 每次 get 时如果有订阅者则添加订阅</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">if</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token plain">Dep</span><span class="token punctuation" style="color:#393A34">.</span><span class="token plain">target</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> dep</span><span class="token punctuation" style="color:#393A34">.</span><span class="token function" style="color:#d73a49">depend</span><span class="token punctuation" style="color:#393A34">(</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">}</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">return</span><span class="token plain"> val</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">}</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token function-variable function" style="color:#d73a49">set</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> </span><span class="token keyword" style="color:#00009f">function</span><span class="token plain"> </span><span class="token function" style="color:#d73a49">reactiveSetter</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token plain">newVal</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> val </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> newVal</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">// 每次更新数据之后广播更新</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> dep</span><span class="token punctuation" style="color:#393A34">.</span><span class="token function" style="color:#d73a49">notify</span><span class="token punctuation" style="color:#393A34">(</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">}</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">}</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token punctuation" style="color:#393A34">}</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><h4 class="anchor anchorWithHideOnScrollNavbar_WYt5" id="22-依赖收集">2.2 依赖收集<a href="#22-依赖收集" class="hash-link" aria-label="Direct link to 2.2 依赖收集" title="Direct link to 2.2 依赖收集"></a></h4><p>Vue 会在需要使用到属性的地方新建一个 Watcher 的实例 watcher，watcher 实例化时会读取对应属性的内容，从而触发 1.1 中的 getter，将 watcher 注册进 Dep 中。</p><p>以下是 Watcher 的伪代码：</p><div class="language-typescript codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#393A34;--prism-background-color:#f6f8fa"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-typescript codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic">/**</span><br></span><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic"> * 为了方便理解，以下代码略有修改，省略了部分不相关内容</span><br></span><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic"> */</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token keyword" style="color:#00009f">export</span><span class="token plain"> </span><span class="token keyword" style="color:#00009f">default</span><span class="token plain"> </span><span class="token keyword" style="color:#00009f">class</span><span class="token plain"> </span><span class="token class-name">Watcher</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> vm</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> Component</span><span class="token punctuation" style="color:#393A34">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> getter</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> </span><span class="token builtin">Function</span><span class="token punctuation" style="color:#393A34">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> value</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> </span><span class="token builtin">any</span><span class="token punctuation" style="color:#393A34">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> cb</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> </span><span class="token builtin">Function</span><span class="token punctuation" style="color:#393A34">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token function" style="color:#d73a49">constructor</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> vm</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> Component</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> exp</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> </span><span class="token builtin">string</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">this</span><span class="token punctuation" style="color:#393A34">.</span><span class="token plain">vm </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> vm</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">this</span><span class="token punctuation" style="color:#393A34">.</span><span class="token plain">cb </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> cb</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">// 获取表达式对应的属性的 getter</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">this</span><span class="token punctuation" style="color:#393A34">.</span><span class="token plain">getter </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> </span><span class="token function" style="color:#d73a49">parsePath</span><span class="token punctuation" style="color:#393A34">(</span><span class="token plain">exp</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">this</span><span class="token punctuation" style="color:#393A34">.</span><span class="token plain">value </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> </span><span class="token keyword" style="color:#00009f">this</span><span class="token punctuation" style="color:#393A34">.</span><span class="token function" style="color:#d73a49">get</span><span class="token punctuation" style="color:#393A34">(</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">}</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">/**</span><br></span><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic"> * 获取最新的值</span><br></span><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic"> **/</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token function" style="color:#d73a49">get</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">// 将 Dep 的当前订阅者指向当前 watcher</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> Dep</span><span class="token punctuation" style="color:#393A34">.</span><span class="token plain">target </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> </span><span class="token keyword" style="color:#00009f">this</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">let</span><span class="token plain"> value</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">const</span><span class="token plain"> vm </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> </span><span class="token keyword" style="color:#00009f">this</span><span class="token punctuation" style="color:#393A34">.</span><span class="token plain">vm</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">// 获取对应属性值</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> value </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> </span><span class="token keyword" style="color:#00009f">this</span><span class="token punctuation" style="color:#393A34">.</span><span class="token function" style="color:#d73a49">getter</span><span class="token punctuation" style="color:#393A34">.</span><span class="token function" style="color:#d73a49">call</span><span class="token punctuation" style="color:#393A34">(</span><span class="token plain">vm</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"> vm</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">// 清空 Dep 当前订阅者</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> Dep</span><span class="token punctuation" style="color:#393A34">.</span><span class="token plain">target </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> </span><span class="token keyword" style="color:#00009f">null</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">return</span><span class="token plain"> value</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">}</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">/**</span><br></span><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic"> * 订阅</span><br></span><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic"> **/</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token function" style="color:#d73a49">addDep</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token plain">dep</span><span class="token operator" style="color:#393A34">:</span><span class="token plain"> Dep</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">// 将当前 watcher 添加到 Dep 的订阅者列表中</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> dep</span><span class="token punctuation" style="color:#393A34">.</span><span class="token function" style="color:#d73a49">addSub</span><span class="token punctuation" style="color:#393A34">(</span><span class="token keyword" style="color:#00009f">this</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">}</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">/**</span><br></span><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic"> * 更新视图</span><br></span><span class="token-line" style="color:#393A34"><span class="token comment" style="color:#999988;font-style:italic"> **/</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token function" style="color:#d73a49">update</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">const</span><span class="token plain"> value </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> </span><span class="token keyword" style="color:#00009f">this</span><span class="token punctuation" style="color:#393A34">.</span><span class="token function" style="color:#d73a49">get</span><span class="token punctuation" style="color:#393A34">(</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">const</span><span class="token plain"> oldValue </span><span class="token operator" style="color:#393A34">=</span><span class="token plain"> </span><span class="token keyword" style="color:#00009f">this</span><span class="token punctuation" style="color:#393A34">.</span><span class="token plain">value</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">// 调用 callback 更新视图</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token keyword" style="color:#00009f">this</span><span class="token punctuation" style="color:#393A34">.</span><span class="token function" style="color:#d73a49">cb</span><span class="token punctuation" style="color:#393A34">.</span><span class="token function" style="color:#d73a49">call</span><span class="token punctuation" style="color:#393A34">(</span><span class="token keyword" style="color:#00009f">this</span><span class="token punctuation" style="color:#393A34">.</span><span class="token plain">vm</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"> value</span><span class="token punctuation" style="color:#393A34">,</span><span class="token plain"> oldValue</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">}</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token punctuation" style="color:#393A34">}</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><h4 class="anchor anchorWithHideOnScrollNavbar_WYt5" id="23-数据更新">2.3 数据更新<a href="#23-数据更新" class="hash-link" aria-label="Direct link to 2.3 数据更新" title="Direct link to 2.3 数据更新"></a></h4><p>state 属性更新时会触发属性的 setter，setter 中会触发 Dep 的更新，Dep 通知 1.2 中收集到的 watcher 更新，watcher 获取到更新的数据之后触发更新视图。</p><h3 class="anchor anchorWithHideOnScrollNavbar_WYt5" id="3-无法监听到的变化">3. 无法监听到的变化<a href="#3-无法监听到的变化" class="hash-link" aria-label="Direct link to 3. 无法监听到的变化" title="Direct link to 3. 无法监听到的变化"></a></h3><p>由于受到 JavaScript 设计的限制，Vue2 使用的 <code>Object.defineProperty</code> 并不能完全劫持所有数据的变化，以下是几种无法正常劫持的变化：</p><ul><li>无法劫持新创建的属性，为了解决这个问题，Vue 提供了 <code>Vue.set</code> 以创建新属性。</li><li>无法劫持数组的变化，为了解决这个问题，Vue 对数组原生方法进行了劫持。</li><li>无法劫持利用索引修改数组元素，这个问题同样可以用 <code>Vue.set</code> 解决。</li></ul><h3 class="anchor anchorWithHideOnScrollNavbar_WYt5" id="4-vue2-与-vue3-的差异">4. Vue2 与 Vue3 的差异<a href="#4-vue2-与-vue3-的差异" class="hash-link" aria-label="Direct link to 4. Vue2 与 Vue3 的差异" title="Direct link to 4. Vue2 与 Vue3 的差异"></a></h3><p>Vue2 与 Vue3 数据绑定机制的主要差异是劫持方式。Vue2 使用的是 <code>Object.defineProperty</code> 而 Vue3 使用的是 <code>Proxy</code>。<code>Proxy</code> 可以创建一个对象的代理，从而实现对这个对象基本操作的拦截和自定义。</p><table><thead><tr><th>特性</th><th>defineProperty</th><th>Proxy</th></tr></thead><tbody><tr><td>劫持新创建属性</td><td>否</td><td>是</td></tr><tr><td>劫持数组变化</td><td>否</td><td>是</td></tr><tr><td>劫持索引修改数组元素</td><td>否</td><td>是</td></tr><tr><td>兼容性</td><td>IE8及以上</td><td>不支持IE</td></tr></tbody></table><p>由于 Vue 3 中改用 Proxy 实现数据劫持，Vue 2 中的 <code>Vue.set/vm.$set</code> 在 Vue 3 中被移除。</p><h2 class="anchor anchorWithHideOnScrollNavbar_WYt5" id="参考资料">参考资料<a href="#参考资料" class="hash-link" aria-label="Direct link to 参考资料" title="Direct link to 参考资料"></a></h2><ol><li><a href="https://vuejs.org/" target="_blank" rel="noopener noreferrer">Vuejs 官网</a></li><li><a href="https://github.com/vuejs/vue" target="_blank" rel="noopener noreferrer">Vuejs 源码</a></li></ol></div></article><nav class="pagination-nav docusaurus-mt-lg" aria-label="Docs pages navigation"><a class="pagination-nav__link pagination-nav__link--prev" href="/awesome-interview/book1/engineer-webpack-workflow"><div class="pagination-nav__sublabel">Previous</div><div class="pagination-nav__label">工程化：webpack 工作流程</div></a><a class="pagination-nav__link pagination-nav__link--next" href="/awesome-interview/book1/frame-vue-computed-watch"><div class="pagination-nav__sublabel">Next</div><div class="pagination-nav__label">框架：Vue 的 computed 和 watch 的区别</div></a></nav></div></div><div class="col col--3"><div class="tableOfContents_bqdL thin-scrollbar theme-doc-toc-desktop"><ul class="table-of-contents table-of-contents__left-border"><li><a href="#相关问题" class="table-of-contents__link toc-highlight">相关问题</a></li><li><a href="#回答关键点" class="table-of-contents__link toc-highlight">回答关键点</a></li><li><a href="#知识点深入" class="table-of-contents__link toc-highlight">知识点深入</a><ul><li><a href="#1-前置概念" class="table-of-contents__link toc-highlight">1. 前置概念</a></li><li><a href="#2-实现原理" class="table-of-contents__link toc-highlight">2. 实现原理</a><ul><li><a href="#21-响应式对象" class="table-of-contents__link toc-highlight">2.1 响应式对象</a></li><li><a href="#22-依赖收集" class="table-of-contents__link toc-highlight">2.2 依赖收集</a></li><li><a href="#23-数据更新" class="table-of-contents__link toc-highlight">2.3 数据更新</a></li></ul></li><li><a href="#3-无法监听到的变化" class="table-of-contents__link toc-highlight">3. 无法监听到的变化</a></li><li><a href="#4-vue2-与-vue3-的差异" class="table-of-contents__link toc-highlight">4. Vue2 与 Vue3 的差异</a></li></ul></li><li><a href="#参考资料" class="table-of-contents__link toc-highlight">参考资料</a></li></ul></div></div></div><div class="row"><div class="col"><div class="react-utterences"><div>Loading script...</div></div></div><div class="col col--3"></div></div></div></main></div></div></div>
|
||
<script src="/awesome-interview/assets/js/runtime~main.a75952d5.js"></script>
|
||
<script src="/awesome-interview/assets/js/main.a5e14537.js"></script>
|
||
</body>
|
||
</html> |