回顾一下，整个建议的 vue 响应式代码中，首先在 vue.js 中存储了传入的参数，然后将 data 中数据都转换为 getter/setter 添加到了 vue 实例上。然后在 observer.js 中将 data 中的属性都转换为 getter/setter，如果属性是对象，则对象下的属性也都要转换成 getter/setter。处理完数据就要开始编译视图，我们遍历视图上所有的节点，将其分为两种类型，文本节点用插值表达式处理，元素节点用指令处理，完成渲染时将视图上用到 data 属性的地方都转换成对应的值。最后利用 dep.js 和 watcher.js 形成观察者模式，做到改变数据的时候同时改变视图。
index.html
<!DOCTYPE html>
<html>
<body>
<div id="app">
<div>差值表达式</div>
<span>{{ msg }}</span>
<span>{{ count }}</span>
<div>v-text</div>
<span v-text="msg"></span>
<div>v-model</div>
<input type="text" v-model="msg">
<input type="text" v-model="count">
</div>
<script src="./dep.js"></script>
<script src="./watcher.js"></script>
<script src="./compiler.js"></script>
<script src="./observer.js"></script>
<script src="./vue.js"></script>
<script>
let vm = new Vue({
el: '#app',
data: {
msg: 'test',
count: 20,
person: {name: 'zs'}
}
})
</script>
</body>
</html>
vue.js
class Vue {
constructor(options) {
this.$options = options || {}
this.$data = options.data || {}
this.$el = typeof options.el === 'string' ? document.querySelector(options.el) : options.el
this._proxyData(this.$data)
new Observer(this.$data)
new Compiler(this)
}
_proxyData(data) {
for (let key in data) {
Object.defineProperty(this, key, {
enumerable: true,
configurable: true,
get() {
return data[key]
},
set(newValue) {
if (newValue === data[key]) return
data[key] = newValue
}
})
}
}
}
observer.js
class Observer {
constructor(data) {
this.walk(data)
}
walk(data) {
if (!data || typeof data !== 'object') return
for(let key in data) {
this.defineReactive(data, key)
}
}
defineReactive(data, key) {
let dep = new Dep()
let value = data[key]
this.walk(value)
const self = this
Object.defineProperty(data, key, {
enumerable: true,
configurable: true,
get() {
Dep.target && dep.addSub(Dep.target)
return value
},
set(newValue) {
if (newValue === value) return
value = newValue
self.walk(newValue)
dep.notify()
}
})
}
}
compiler.js
class Compiler {
constructor (vm) {
this.vm = vm
this.compiler(vm.$el)
}
compiler(el) {
let childNodes = el.childNodes
Array.from(childNodes).forEach(node => {
if (this.isTextNode(node)) {
this.compilerText(node)
} else if (this.isElementNode(node)) {
this.compilerElement(node)
}
if (node.childNodes && node.childNodes.length) {
this.compiler(node)
}
})
}
compilerText(node) {
// 文本节点替换插值表达式
let value = node.textContent
let reg = /\{\{(.+?)\}\}/
let key = ''
if (reg.test(value)) {
value.replace(reg, (match, p1) => {
key = p1.trim()
node.textContent = this.vm[key]
})
new Watcher(this.vm, key, (newValue) => {
node.textContent = newValue
})
}
}
compilerElement(node) {
// 指令解析属性节点
Array.from(node.attributes).forEach(attr => {
let attrName = attr.name
if (this.isDirective(attrName)) {
let attrValue = attr.value
this.update(node, attrName, attrValue)
}
})
}
// 用拼接指令名和 'Updater' 的方式为不同的指令操作方法命名
update(node, attrName, key) {
attrName = attrName.substr(2)
let updateFn = this[attrName + 'Updater']
updateFn && updateFn.call(this, node, this.vm[key], key)
}
textUpdater(node, value, key) {
node.textContent = value
new Watcher(this.vm, key, (newValue) => {
node.textContent = newValue
})
}
modelUpdater(node, value, key) {
node.value = value
new Watcher(this.vm, key, (newValue) => {
node.value = newValue
})
// 双向绑定
node.addEventListener('input', () => {
this.vm[key] = node.value
})
}
isTextNode(node) {
return node.nodeType === 3
}
isElementNode(node) {
return node.nodeType === 1
}
isDirective(attrName) {
return attrName.startsWith('v-')
}
}
dep.js
class Dep {
constructor () {
this.subs = []
}
// 收集依赖
addSub (sub) {
if (sub && sub.update) {
this.subs.push(sub)
}
}
// 发送通知
notify() {
this.subs.forEach(sub => {
sub.update()
})
}
}
watcher.js
class Watcher {
constructor(vm, key, cb) {
this.vm = vm
this.key = key
this.cb = cb
Dep.target = this
this.oldValue = vm[key]
Dep.target = null
}
update() {
let newValue = this.vm[this.key]
if (newValue === this.oldValue) return
this.cb(newValue)
}
}
