DOM nyata atau nyata
DOM
singkatan dari Document Object Model
(Document Object Model). Sederhananya, DOM adalah representasi dari antarmuka pengguna (UI) dalam sebuah aplikasi. Setiap kali UI berubah, DOM juga diperbarui untuk mencerminkan perubahan tersebut. Manipulasi DOM yang sering berdampak negatif pada kinerja.
DOM ?
DOM . DOM . ( ) () UI . — . , UI, DOM.
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, 10 . . . 10 , ! 1 , 9 .
— , - DOM. . React (virtual) DOM (VDOM).
DOM
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VDOM ?
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React VDOM?
, , VDOM, , React.
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React UI (state). , React VDOM. VDOM, React . « » (diffing).
, VDOM, React RDOM. DOM. React JavaScript.
2. React (batch) RDOM
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3. React
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key
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DOM.
componentWillUnmount()
. , DOM DOM.UNSAFE_componentWillMount()
,componentDidMount()
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<div> <Counter /> </div> <span> <Counter /> </span>
Counter
.
, React «» . DOM , . :
<div className="before" title="stuff" /> <div className="after" title="stuff" />
className
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, , :
<ul>
<li></li>
<li></li>
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<ul>
<li></li>
<li></li>
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</ul>
React "", <li></li>
<li></li>
, <li></li>
.
, . , :
<ul>
<li></li>
<li></li>
</ul>
<ul>
<li></li>
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.
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. , React . , :
<ul>
<li key="1"></li>
<li key="2"></li>
</ul>
<ul>
<li key="0"></li>
<li key="1"></li>
<li key="2"></li>
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React , 0
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2
.
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<li key={item.id}>{item.name}</li>
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— , React 16. VDOM.
VDOM?
« DOM» (). , VDOM — JavaScript-.
, DOM-:
:
const vdom = { tagName: 'html', children: [ { tagName: 'head' }, { tagName: 'body', children: [ { tagName: 'ul', attributes: { class: 'list' }, children: [ { tagName: 'li', attributes: { class: 'list_item' }, textContent: ' ', }, // li ], }, // ul ], }, // body ], } // html
VDOM. RDOM, HTML- (). , , , RDOM .
, . , list
, :
const list = { tagName: 'ul', attributes: { class: 'list' }, children: [ { tagName: 'li', attributes: { class: 'list_item' }, textContent: ' ', }, ], }
VDOM
, VDOM .
, VDOM , DOM. , DOM API.
, VDOM , . DOM API, .
const copy = { tagName: 'ul', attributes: { class: 'list' }, children: [ { tagName: 'li', attributes: { class: 'list_item' }, textContent: ' ', }, { tagName: 'li', attributes: { class: 'list_item' }, textContent: ' ', }, ], }
«» (diff) VDOM (list
) . Diff
:
const diffs = [ { newNode: { /* */ }, oldNode: { /* */ }, index: { /* */ }, }, { newNode: { /* */ }, index: { /* ... */ }, }, ]
diff
RDOM. DOM .
, , :
const domElement = document.quesrySelector('list') diffs.forEach((diff) => { const newElement = document.createElement(diff.newNode.tagName) /* ... */ if (diff.oldNode) { // , domElement.replaceChild(diff.newNode, diff.oldNode) } else { // , domElement.append(diff.newNode) } })
, , VDOM.
VDOM
, VDOM .
VDOM , React Vue DOM. , React list
:
import React from 'react' import ReactDOM from 'react-dom' const list = React.createElement( 'ul', { className: 'list' }, React.createElement('li', { className: 'list_item' }, ' ') ) // React «JSX» // const list = <ul className="list"><li className="list_item"> </li></ul> ReactDOM.render(list, document.body)
ReactDOM.render()
:
const newList = React.createElement( 'ul', { className: 'list' }, React.createElement( 'li', { className: 'list_item' }, ' ' ), React.createElement('li', { className: 'list_item' }, ' ') ) const timerId = setTimeout(() => { ReactDOM.render(newList, document.body) clearTimeout(timerId) }, 5000)
React VDOM, , , .
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, Angular
, , (single page applications, SPA) , Dirty Model Checking
( ). , DMC VDOM . MVC- . React , React — , , (view).
VDS .
10% !
