为什么要学习源码

1.可以提升自己学习更优秀的API设计和代码逻辑

2.面试的时候也会经常问源码相关的东西

3.更快的掌握vue和遇到问题可以定位

介绍虚拟DOM

虚拟DOM就是通过JS来生成一个AST节点树

Vue Template Explorer

为什么要有虚拟DOM？

我们可以通过下面的例子

let div = document.createElement('div')
let str = ''
for (const key in div) {
  str += key + ''
}
console.log(str)

发现一个dom上面的属性是非常多的

aligntitlelangtranslatedirhiddenaccessKeydraggablespellcheckautocapitalizecontentEditableisContentEditableinputModeoffsetParentoffsetTopoffsetLeftoffsetWidthoffsetHeightstyleinnerTextouterTextonbeforexrselectonabortonbluroncanceloncanplayoncanplaythroughonchangeonclickoncloseoncontextmenuoncuechangeondblclickondragondragendondragenterondragleaveondragoverondragstartondropondurationchangeonemptiedonendedonerroronfocusonformdataoninputoninvalidonkeydownonkeypressonkeyuponloadonloadeddataonloadedmetadataonloadstartonmousedownonmouseenteronmouseleaveonmousemoveonmouseoutonmouseoveronmouseuponmousewheelonpauseonplayonplayingonprogressonratechangeonresetonresizeonscrollonsecuritypolicyviolationonseekedonseekingonselectonslotchangeonstalledonsubmitonsuspendontimeupdateontoggleonvolumechangeonwaitingonwebkitanimationendonwebkitanimationiterationonwebkitanimationstartonwebkittransitionendonwheelonauxclickongotpointercaptureonlostpointercaptureonpointerdownonpointermoveonpointeruponpointercancelonpointeroveronpointeroutonpointerenteronpointerleaveonselectstartonselectionchangeonanimationendonanimationiterationonanimationstartontransitionrunontransitionstartontransitionendontransitioncanceloncopyoncutonpastedatasetnonceautofocustabIndexattachInternalsblurclickfocusenterKeyHintvirtualKeyboardPolicyonpointerrawupdatenamespaceURIprefixlocalNametagNameidclassNameclassListslotattributesshadowRootpartassignedSlotinnerHTMLouterHTMLscrollTopscrollLeftscrollWidthscrollHeightclientTopclientLeftclientWidthclientHeightattributeStyleMaponbeforecopyonbeforecutonbeforepasteonsearchelementTimingonfullscreenchangeonfullscreenerroronwebkitfullscreenchangeonwebkitfullscreenerrorchildrenfirstElementChildlastElementChildchildElementCountpreviousElementSiblingnextElementSiblingafteranimateappendattachShadowbeforeclosestcomputedStyleMapgetAttributegetAttributeNSgetAttributeNamesgetAttributeNodegetAttributeNodeNSgetBoundingClientRectgetClientRectsgetElementsByClassNamegetElementsByTagNamegetElementsByTagNameNSgetInnerHTMLhasAttributehasAttributeNShasAttributeshasPointerCaptureinsertAdjacentElementinsertAdjacentHTMLinsertAdjacentTextmatchesprependquerySelectorquerySelectorAllreleasePointerCaptureremoveremoveAttributeremoveAttributeNSremoveAttributeNodereplaceChildrenreplaceWithrequestFullscreenrequestPointerLockscrollscrollByscrollIntoViewscrollIntoViewIfNeededscrollTosetAttributesetAttributeNSsetAttributeNodesetAttributeNodeNSsetPointerCapturetoggleAttributewebkitMatchesSelectorwebkitRequestFullScreenwebkitRequestFullscreenariaAtomicariaAutoCompleteariaBusyariaCheckedariaColCountariaColIndexariaColSpanariaCurrentariaDescriptionariaDisabledariaExpandedariaHasPopupariaHiddenariaKeyShortcutsariaLabelariaLevelariaLiveariaModalariaMultiLineariaMultiSelectableariaOrientationariaPlaceholderariaPosInSetariaPressedariaReadOnlyariaRelevantariaRequiredariaRoleDescriptionariaRowCountariaRowIndexariaRowSpanariaSelectedariaSetSizeariaSortariaValueMaxariaValueMinariaValueNowariaValueTextgetAnimationsnodeTypenodeNamebaseURIisConnectedownerDocumentparentNodeparentElementchildNodesfirstChildlastChildpreviousSiblingnextSiblingnodeValuetextContentELEMENT_NODEATTRIBUTE_NODETEXT_NODECDATA_SECTION_NODEENTITY_REFERENCE_NODEENTITY_NODEPROCESSING_INSTRUCTION_NODECOMMENT_NODEDOCUMENT_NODEDOCUMENT_TYPE_NODEDOCUMENT_FRAGMENT_NODENOTATION_NODEDOCUMENT_POSITION_DISCONNECTEDDOCUMENT_POSITION_PRECEDINGDOCUMENT_POSITION_FOLLOWINGDOCUMENT_POSITION_CONTAINSDOCUMENT_POSITION_CONTAINED_BYDOCUMENT_POSITION_IMPLEMENTATION_SPECIFICappendChildcloneNodecompareDocumentPositioncontainsgetRootNodehasChildNodesinsertBeforeisDefaultNamespaceisEqualNodeisSameNodelookupNamespaceURIlookupPrefixnormalizeremoveChildreplaceChildaddEventListenerdispatchEventremoveEventListener

所以直接操作DOM非常浪费性能

解决方案就是 我们可以用JS的计算性能来换取操作DOM所消耗的性能，既然我们逃不掉操作DOM这道坎,但是我们可以尽可能少的操作DOM

操作JS是非常快的

介绍Diff算法

Vue3 源码地址 https://github.com/vuejs/core

详细解说可以观看视频讲解 小满zs的个人空间_哔哩哔哩_Bilibili

<template>
  <div>
    <div :key="item" v-for="(item) in Arr">{{ item }}</div>
  </div>
</template>



<script setup lang="ts">
const Arr: Array<string> = ['A', 'B', 'C', 'D']
Arr.splice(2,0,'DDD')
</script>


<style>
</style>

splice 用法 太贴心了