现在mvvm框架火得不行，小编我最近也开始研究vue，相比jquery框架，vue的面向数据编程的确可以让我们摆脱操作dom的痛苦专注逻辑本身。
javascript
无论学什么框架，我都喜欢研究底层的东西，vue最核心的功能就是双向绑定，经过几天研究，同javascript实现了一个双向绑定功能。
双向数据绑定底层的思想非常的基本，分为三个步骤：
1.需要一个方法来识别哪个UI元素被绑定了相应的属性
2.需要监视属性和UI元素的变化
3.需要将所有变化传播到绑定的对象和元素
方法一：利用发布订阅模式，订阅数据变更
Html代码：
<div class="app"> <input type="text" data-bind-id="demo"> <p data-id="demo"></p> </div>
javascript代码
function DataBinder(object_id) { //创建一个简单地PubSub对象 var pubSub = { callbacks: {}, on: function (msg, callback) { this.callbacks[msg] = this.callbacks[msg] || []; this.callbacks[msg].push(callback); }, publish: function (msg) { this.callbacks[msg] = this.callbacks[msg] || []; for (var i = 0, len = this.callbacks[msg].length; i < len; i ) { this.callbacks[msg][i].apply(this, Array.prototype.slice.call(arguments, 1)); } } }; var data_attr = "data-bind-" object_id, view_attr = 'data-' object_id, message = object_id ":change"; var changeHandler = function (e) { var target = e.target || e.srcElemnt, //IE8兼容 prop_name = target.getAttribute(data_attr); if (prop_name && prop_name !== "") { pubSub.publish(message, target, prop_name, target.value); } }; //监听变化事件并代理到PubSub if (document.addEventListener) { document.addEventListener("keyup", changeHandler, false); } else { //IE8使用attachEvent而不是addEventListener document.attachEvent("keyup", changeHandler); } //PubSub将变化传播到所有绑定元素 pubSub.on(message, function (event, prop_name, new_val) { var elements = document.querySelectorAll("[" view_attr "=" prop_name "]"), tag_name; for (var i = 0, len = elements.length; i < len; i ) { tag_name = elements[i].tagName.toLowerCase(); if (tag_name === "input" || tag_name === "textarea" || tag_name === "select") { elements[i].value = new_val; } else { elements[i].innerHTML = new_val; } } }); return pubSub; } DataBinder('id');
方法二：数据劫持 。
html代码：
<div class="app"> <input type="demo" h-model="demo" spellcheck="true"> <p h-text="demo"></p> </div>
借助 Object.defineProperty 方法， Object.defineProperty 方法可以为任何已存在的属性重新定义get与set方法。
(function(window, undefined) { var addEvent = (function () { if(window.addEventListener) { return function (el, type, fn) { if(el && el.nodeName || el === window) { el.addEventListener(type, fn, false) }else if(el.length) { for(var item of el) { addEvent(item, type, fn); } } } }else { return function (el, type, fn) { if(el && el.nodeName || el === window) { el.attachEvent('on' type, function () { return fn.call(el, event); }) }else if(el.length) { for(var item of el) { addEvent(item, type, fn); } } } } })(); var Hue = function(opt) { var el = document.querySelector(opt.el); var data = opt.data || {}; this.el = el; this.data = data; this.bindText(); this.bindModel(); return this; }; Hue.prototype = { constructor: Hue, // **前端数据劫持** defineObj: function(obj, prop, value) { var _value = value || '', _this = this; try { Object.defineProperty(obj, prop, { get: function() { return _value; }, set: function(newVal) { _value = newVal; _this.bindText(); }, enumerable: true, configurable: true }); } catch (error) { // IE8 才开始支持defineProperty,这也是Vue.js不支持IE8的原因 console.log("Browser must be IE8 !"); } }, bindModel: function() { var modelDOMs = this.el.querySelectorAll('[h-model]'), lenModel = modelDOMs.length; var _this = this, i, propModel; for (i = 0; i < lenModel; i ) { propModel = modelDOMs[i].getAttribute('h-model'); //init value modelDOMs[i].value = this.data[propModel] || ''; // 前端数据劫持 this.defineObj(this.data, propModel); } addEvent(modelDOMs, 'keyup', function (e) { _this.data[propModel] = e.target.value; }) }, bindText: function() { var textDOMs = this.el.querySelectorAll('[h-text]'), lenText = textDOMs.length, prppText, j; for (j = 0; j < lenText; j ) { propText = textDOMs[j].getAttribute('h-text'); textDOMs[j].innerHTML = this.data[propText] || ''; } } }; window.Hue = Hue; })(window); // test... new Hue({ el: '.app', data: { demo: 'Kenny' } });
欢迎大家关注和转发。
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