<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>事件与代码优化</title>
</head>
<body>
<div id="app" >
<input v-model="name" v-on:click="sayHi" type="text">
<h1>{{name}} 's age is {{age}}</h1>
</div>
<script>
function observe(data) {
if(!data || typeof data !== 'object') return
for(var key in data) {
let val = data[key]
let subject = new Subject()
Object.defineProperty(data, key, {
enumerable: true,
configurable: true,
get: function() {
console.log(`get ${key}: ${val}`)
if(currentObserver){
console.log('has currentObserver')
currentObserver.subscribeTo(subject)
}
return val
},
set: function(newVal) {
val = newVal
console.log('start notify...')
subject.notify()
}
})
if(typeof val === 'object'){
observe(val)
}
}
}
let id = 0
let currentObserver = null
class Subject {
constructor() {
this.id = id++
this.observers = []
}
addObserver(observer) {
this.observers.push(observer)
}
removeObserver(observer) {
var index = this.observers.indexOf(observer)
if(index > -1){
this.observers.splice(index, 1)
}
}
notify() {
this.observers.forEach(observer=> {
observer.update()
})
}
}
class Observer{
constructor(vm, key, cb) {
this.subjects = {}
this.vm = vm
this.key = key
this.cb = cb
this.value = this.getValue()
}
update(){
let oldVal = this.value
let value = this.getValue()
if(value !== oldVal) {
this.value = value
this.cb.bind(this.vm)(value, oldVal)
}
}
subscribeTo(subject) {
if(!this.subjects[subject.id]){
console.log('subscribeTo.. ', subject)
subject.addObserver(this)
this.subjects[subject.id] = subject
}
}
getValue(){
currentObserver = this
let value = this.vm[this.key] //等同于 this.vm.$data[this.key]
currentObserver = null
return value
}
}
class Compile {
constructor(vm){
this.vm = vm
this.node = vm.$el
this.compile()
}
compile(){
this.traverse(this.node)
}
traverse(node){
if(node.nodeType === 1){
this.compileNode(node) //解析节点上的v-bind 属性
node.childNodes.forEach(childNode=>{
this.traverse(childNode)
})
}else if(node.nodeType === 3){ //处理文本
this.compileText(node)
}
}
compileText(node){
let reg = /{{(.+?)}}/g
let match
console.log(node)
while(match = reg.exec(node.nodeValue)){
let raw = match[0]
let key = match[1].trim()
node.nodeValue = node.nodeValue.replace(raw, this.vm[key])
new Observer(this.vm, key, function(val, oldVal){
node.nodeValue = node.nodeValue.replace(oldVal, val)
})
}
}
//处理指令
compileNode(node){
let attrs = [...node.attributes] //类数组对象转换成数组，也可用其他方法
attrs.forEach(attr=>{
//attr 是个对象，attr.name 是属性的名字如 v-model， attr.value 是对应的值，如 name
if(this.isModelDirective(attr.name)){
this.bindModel(node, attr)
}else if(this.isEventDirective(attr.name)){
this.bindEventHander(node, attr)
}
})
}
bindModel(node, attr){
let key = attr.value //attr.value === 'name'
node.value = this.vm[key]
new Observer(this.vm, key, function(newVal){
node.value = newVal
})
node.oninput = (e)=>{
this.vm[key] = e.target.value //因为是箭头函数，所以这里的 this 是 compile 对象
}
}
bindEventHander(node, attr){ //attr.name === 'v-on:click', attr.value === 'sayHi'
let eventType = attr.name.substr(5) // click
let methodName = attr.value
node.addEventListener(eventType, this.vm.$methods[methodName])
}
//判断属性名是否是指令
isModelDirective(attrName){
return attrName === 'v-model'
}
isEventDirective(attrName){
return attrName.indexOf('v-on') === 0
}
}
class mvvm {
constructor(opts) {
this.init(opts)
observe(this.$data)
new Compile(this)
}
init(opts){
this.$el = document.querySelector(opts.el)
this.$data = opts.data || {}
this.$methods = opts.methods || {}
//把$data 中的数据直接代理到当前 vm 对象
for(let key in this.$data) {
Object.defineProperty(this, key, {
enumerable: true,
configurable: true,
get: ()=> { //这里用了箭头函数，所有里面的 this 就指代外面的 this 也就是 vm
return this.$data[key]
},
set: newVal=> {
this.$data[key] = newVal
}
})
}
//让 this.$methods 里面的函数中的 this，都指向当前的 this，也就是 vm
for(let key in this.$methods) {
this.$methods[key] = this.$methods[key].bind(this)
}
}
}
let vm = new mvvm({
el: '#app',
data: {
name: 'jirengu',
age: 3
},
methods: {
sayHi(){
alert(`hi ${this.name}` )
}
}
})
let clock = setInterval(function(){
vm.age++ //等同于 vm.$data.age， 见 mvvm init 方法内的数据劫持
if(vm.age === 10) clearInterval(clock)
}, 1000)
</script>
</body>
</html>
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