手動觸發綁定
手動觸發指令綁定是比較直接的實現方式，主要思路是通過在數據對象上定義get()方法和set()方法，調用時手動觸發get()或set()函數來獲取、修改數據，改變數據後會主動觸發get()和set()函數中View層的重新渲染功能。根據View來驅動ViewModel變化的場景主要應用於<input>、<select>、<textarea> 等元素，當用戶輸入內容變化時，通過監聽DOM的change，select、keyup等事件來觸發操作改變ViewModel的數據。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<body>
<input q-value="value" type="text" id="input">
<span q-text="value" id="el"></span>
<script>
let elems=[document.getElementById('input'),document.getElementById('el')];
let data={value:'hello'};
let directive={
text:function (text) {
this.innerHTML=text;
},
value:function (value) {
this.setAttribute('value',value);
}
}
function scan() {
for(let elem of elems){
elem.directive=[];
for(let attr of elem.attributes){
if(attr.nodeName.indexOf('q-')>=0){
directive[attr.nodeName.slice(2)].call(elem,data[attr.nodeValue]);
elem.directive.push(attr.nodeName.slice(2));
}
}
}
}
function ViewModelSet(key,value) {
data[key]=value;
scan();
}
scan();
setTimeout(function () {
ViewModelSet('value','helloouvenzhang');
},1000);
if(document.addEventListener){
elems[0].addEventListener('keyup',function (e) {
ViewModelSet('value',e.target.value);
},false);
}
</script>
</body>
</html>前端數據對象挾持
其基本思路是使用Object.defineProperty和Object.defineProperties對ViewModel數據對象進行屬性get()和set()的監聽，當有數據讀取和賦值操作時則掃描元素節點，運行對應節點的Directive指令。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<body>
<input q-value="value" type="text" id="input">
<div q-text="value" id="el"></div>
<script>
let elems=[document.getElementById('el'),document.getElementById('input')];
let data={value:'hello'};
let directive={
text:function (text) {
this.innerHTML=text;
},
value:function (value) {
this.setAttribute('value',value);
}
};
let bValue;
scan();
defineGetAndSet(data,'value');
if(document.addEventListener){
elems[1].addEventListener('keyup',function (e) {
data.value=e.target.value;
},false);
} else {
elems[1].attachEvent('onkeyup',function (e) {
data.value=e.srcElement.value;
},false);
}
setTimeout(function () {
data.value='helloouvenzhang';
},2000);
function scan() {
for(let elem of elems){
elem.directive=[];
for(let attr of elem.attributes){
if(attr.nodeName.indexOf('q-')>=0){
directive[attr.nodeName.slice(2)].call(elem,data[attr.nodeValue]);
elem.directive.push(attr.nodeName.slice(2));
}
}
}
}
function defineGetAndSet(obj,propName) {
Object.defineProperty(obj,propName,{
get:function () {
return bValue;
},
set:function (newValue) {
bValue=newValue;
scan();
},
enumerable:true,
configurable:true
})
}
</script>
</body>
</html>ES6 Proxy
Proxy特性可以用於在已有的對象基礎上重新定義一個對象，並重新定義對象原型上的方法，包括get()和set()方法。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<body>
<input q-value="value" type="text" id="input">
<span q-text="value" id="el"></span>
<script>
let elems=[document.getElementById('el'),document.getElementById('input')];
let directive={
text:function (text) {
this.innerHTML=text;
},
value:function (value) {
this.setAttribute('value',value);
}
};
let data = new Proxy({},{
get:function (target,key,receiver) {
return target.value;
},
set:function (target,key,value,receiver) {
target.value=value;
scan();
return target.value;
}
});
data['value']='hello';
scan();
if(document.addEventListener){
elems[1].addEventListener('keyup',function (e) {
data.value=e.target.value;
},false);
} else {
elems[1].attachEvent('onkeyup',function (e) {
data.value=e.srcElement.value;
},false);
}
setTimeout(function () {
data.value='hello ouvenzhang';
},1000);
function scan() {
for(let elem of elems){
elem.direction=[];
for(let attr of elem.attributes){
if(attr.nodeName.indexOf('q-')>=0){
directive[attr.nodeName.slice(2)].call(elem,data[attr.nodeValue]);
elem.directive.push(attr.nodeName.slice(2));
}
}
}
}
</script>
</body>
</html>vue.js實現原理
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Two-way data-binding</title>
</head>
<body>
<div id="app">
<input type="text" v-model="text">
{{ text }}
</div>
<script>
function observe (obj, vm) {
Object.keys(obj).forEach(function (key) {
defineReactive(vm, key, obj[key]);
});
}
function defineReactive (obj, key, val) {
var dep = new Dep();
Object.defineProperty(obj, key, {
get: function () {
if (Dep.target) dep.addSub(Dep.target);
return val
},
set: function (newVal) {
if (newVal === val) return
val = newVal;
dep.notify();
}
});
}
function nodeToFragment (node, vm) {
var flag = document.createDocumentFragment();
var child;
while (child = node.firstChild) {
compile(child, vm);
flag.appendChild(child);
}
return flag;
}
function compile (node, vm) {
var reg = /\{\{(.*)\}\}/;
// 節點類型爲元素
if (node.nodeType === 1) {
var attr = node.attributes;
// 解析屬性
for (var i = 0; i < attr.length; i++) {
if (attr[i].nodeName == 'v-model') {
var name = attr[i].nodeValue; // 獲取v-model綁定的屬性名
node.addEventListener('input', function (e) {
// 給相應的data屬性賦值，進而觸發該屬性的set方法
vm[name] = e.target.value;
});
node.value = vm[name]; // 將data的值賦給該node
node.removeAttribute('v-model');
}
}
new Watcher(vm, node, name, 'input');
}
// 節點類型爲text
if (node.nodeType === 3) {
if (reg.test(node.nodeValue)) {
var name = RegExp.$1; // 獲取匹配到的字符串
name = name.trim();
new Watcher(vm, node, name, 'text');
}
}
}
function Watcher (vm, node, name, nodeType) {
// this爲watcher函數
Dep.target = this;
// console.log(this);
this.name = name;
this.node = node;
this.vm = vm;
this.nodeType = nodeType;
this.update();
Dep.target = null;
}
Watcher.prototype = {
update: function () {
this.get();
if (this.nodeType == 'text') {
this.node.nodeValue = this.value;
}
if (this.nodeType == 'input') {
this.node.value = this.value;
}
},
// 獲取daa中的屬性值
get: function () {
this.value = this.vm[this.name]; // 觸發相應屬性的get
}
}
function Dep () {
this.subs = []
}
Dep.prototype = {
addSub: function(sub) {
this.subs.push(sub);
},
notify: function() {
this.subs.forEach(function(sub) {
sub.update();
});
}
};
function Vue (options) {
this.data = options.data;
var data = this.data;
observe(data, this);
var id = options.el;
var dom = nodeToFragment(document.getElementById(id), this);
// 編譯完成後，將dom返回到app中
document.getElementById(id).appendChild(dom);
}
var vm = new Vue({
el: 'app',
data: {
text: 'hello world'
}
});
</script>
</body>
</html>
