vue双向绑定笔记
原文：https://github.com/louzhedong/blog/issues/4
<!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>Document</title>
</head>
<body>
<div id="app">
<form>
<input type="text" v-model="number">
<button type="button" v-click="increment">增加</button>
</form>
<h3 v-bind="number"></h3>
</div>
<script>
function myVue(options) {
this._init(options)
}
myVue.prototype._init = function (options) { // 参数 el: '#app',data: {number: 0},methods: {increment: function () {this.number++}}
this.$options = options
this.$el = document.querySelector(options.el) // 找到指定元素
this.$data = options.data // data中的数据结构，如number:0
this.$methods = options.methods // methods中的数据结构，如increment:function(){this.number++}
this._binding = {}
this._obverse(this.$data)
this._complie(this.$el)
}
myVue.prototype._obverse = function (obj) { // data结构，如number:0
var _this = this
Object.keys(obj).forEach(function (key) { // Object.keys()返回对象的Key
if (obj.hasOwnProperty(key)) { // 对象是否包含指定属性,返回boolean
_this._binding[key] = {
_directives: []
}
console.log(_this._binding[key])
var value = obj[key]
if (typeof value === 'object') { // 如果还是对象继续遍历
_this._obverse(value)
}
var binding = _this._binding[key]
// 定义属性描述 参数一定义属性的对象，参数二定义属性名称，参数三属性描述
Object.defineProperty(_this.$data, key, {
enumerable: true, // 开启才能出现在对象的枚举属性中
configurable: true, // 开启属性描述才能改变，同时属性能删除
get: function () { // 给属性提供getter方法
console.log(`${key}获取${value}`)
return value
},
set: function (newVal) { // 给属性提供setter方法
console.log(`${key}更新${value}`)
if (value !== newVal) {
value = newVal
binding._directives.forEach(function (item) {
item.update()
})
}
}
})
}
})
}
myVue.prototype._complie = function (root) {
var _this = this
var nodes = root.children
for (var i = 0; i < nodes.length; i++) {
var node = nodes[i]
if (node.children.length) {
this._complie(node)
}
if (node.hasAttribute('v-click')) {
node.onclick = (function () {
var attrVal = nodes[i].getAttribute('v-click')
return _this.$methods[attrVal].bind(_this.$data)
})()
}
if (node.hasAttribute('v-model') && (node.tagName == 'INPUT' || node.tagName == 'TEXTAREA')) {
node.addEventListener('input', (function (key) {
var attrVal = node.getAttribute('v-model')
_this._binding[attrVal]._directives.push(new Watcher(
'input',
node,
_this,
attrVal,
'value'
))
return function () {
_this.$data[attrVal] = nodes[key].value
}
})(i))
}
if (node.hasAttribute('v-bind')) {
var attrVal = node.getAttribute('v-bind')
_this._binding[attrVal]._directives.push(new Watcher(
'text',
node,
_this,
attrVal,
'innerHTML'
))
}
}
}
function Watcher(name, el, vm, exp, attr) {
this.name = name // 指令名称，如文本节点text
this.el = el // 指令对应DOM元素
this.vm = vm // 指令所属myVue实例
this.exp = exp // 指令对应值，如number
this.attr = attr // 指令属性值，如innerHTML
this.update()
}
Watcher.prototype.update = function () {
this.el[this.attr] = this.vm.$data[this.exp] // 触发值改变，会调属性get方法
}
window.onload = function () { // 页面初始化创建实例
var app = new myVue({
el: '#app',
data: {
number: 0
},
methods: {
increment: function () {
this.number++
}
}
})
}
</script>
</body>
</html>
