<div id="app">
    <div>
        <div v-text="myText"></div>
        <div v-text="myBox"></div>
        <input type="text" v-model="myText">
    </div>
</div>

JS:仿vue数据初始化

const app = new Vue({
    el:'#app',
    data:{
        myText:'数据响应式',
        myBox:'我是一个盒子'
    }
})

核心：发布订阅者模式

//      发布订阅者设计模式
//      发布者化整为零，
        class Vue{
            constructor(options){
                this.options = options;
                this.$data = options.data;
                this.$el = document.querySelector(options.el);
                this._directive = {}; 
                
                this.Observer(this.$data);
                this.Complie(this.$el);
            }
            //劫持数据
            Observer(data){
                for( let key in data ){
                    this._directive[key] = [];
                    console.log(this._directive)
                    let Val = data[key];
                    let watch = this._directive[key];
                    Object.defineProperty(this.$data, key, {
                        get : function(){
                            return Val;
                        },
                        set : function(newVal){
                            if( newVal !== Val ){//新值不等于老值
                                Val = newVal;
                                //更新视图
                                console.log(watch,'watch')
                                watch.forEach(element => {
                                    element.update();
                                })
                            }
                        }
                    })
                }
            }
            //解析指令
            Complie(el){
                let nodes = el.children;
                for(let i = 0;i < nodes.length; i++){
                    let node = nodes[i];
                    if( nodes[i].children){
                        this.Complie(nodes[i]);
                    }
                    if(node.hasAttribute("v-text")){
//                      console.log(1)
                        let attrVal = node.getAttribute('v-text');
                        this._directive[attrVal].push(new Watcher(node,this,attrVal,'innerHTML'));
//                      console.log(this._directive);
                    }
                    if(node.hasAttribute("v-model")){
                        let attrVal = node.getAttribute('v-model');
                        this._directive[attrVal].push(new Watcher(node,this,attrVal,'value'));
//                      console.log(this._directive);
                        node.addEventListener('input',(function(){
                            return function(){
                                console.log(1);
                                this.$data[attrVal] = node.value;
                            }
                        })().bind(this));
                        
                    }
                }
            }
        }
//      订阅者
        class Watcher{
//          div.innerHTML = vue对象.$data['myText'];
            constructor(el, vm, exp, attr){
                this.el = el;
                this.vm = vm;
                this.exp = exp;
                this.attr = attr;
                this.update();
            }
            update(){
                this.el[this.attr] = this.vm.$data[this.exp];
            }