虚拟DOM的增删改查（粗糙版）
代码如下：
html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>v-doem-es6</title>
</head>
<body>
<div id="root"></div>
<button id="button">change</button>
</body>
<script src="./v-dom-es6.js"></script>
</html>
js
class VNode {
constructor(tag, children, text) {
this.tag = tag
this.children = children
this.text = text
}
render() {
if (this.tag === '#text') {
return document.createTextNode(this.text)
}
let el = document.createElement(this.tag)
this.children.forEach(vChild => {
el.appendChild(vChild.render())
})
return el
}
}
function v(tag, children, text) {
if (typeof children === 'string') {
text = children
children = []
}
return new VNode(tag, children, text)
}
document.querySelector('#button').onclick = function () {
root.innerHTML = ''
root.appendChild(vNodes2.render())
}
function patchElement(parent, newVNode, oldVNode, index = 0) {
if (!oldVNode) {
parent.appendChild(newVNode.render())
} else if (!newVNode) {
parent.removeChild(parent.childNodes[index])
} else if (newVNode.tag !== oldVNode.tag || newVNode.text !== oldVNode.text) {
parent.replaceChild(newVNode.render(), parent.childNodes[index])
} else {
for (let i = 0; i < newVNode.children.length || i < oldVNode.children.length; i++) {
patchElement(parent.childNodes[index], newVNode.children[i], oldVNode.children[i], i)
}
}
}
/*
let vNodes1 = v('div', [
v('p', [
v('span', [v('#text',
]),
v('span', [
v('#text',
])
])
let vNodes2 = v('div', [
v('p', [
v('span', [v('#text',
]),
v('span', [
v('#text',
v('#text', 'zhangyongwang')
])
])
*/
let vNode1 = v('div', [v('#text', 'hello')])
let vNode2 = v('div', [v('#text', 'zhangyongwang')])
const root = document.querySelector('#root')
patchElement(root, vNode1)
patchElement(root, vNode2, vNode1)