如何实现两个input框的同步更新

class MVVM {
    constructor(options) {
        this.$options = options;
        this.$el = options.el;
        this.$data = options.data;
        this.observe(this.$data);
        new Compile(this);
    }
    observe(data) {
        if (!data || typeof data !== 'object') {
            return;
        }
        Object.keys(data).forEach(key => {
            this.defineReactive(data, key, data[key]);
        })
    }
    defineReactive(data, key, value) {
        let dep = new Dep();
        Object.defineProperty(data, key, {
            configurable: false,
            enumerable: true,
            get: () => {
                Dep.target && dep.add(Dep.target);
                return value;
            },
            set: (newVal) => {
                if (newVal === value) { return; }
                value = newVal;
                dep.notify();
            }
        })
    }
}
class Dep {
    constructor() {
        this.deps = [];
    }
    add(dep) {
        this.deps.push(dep);
    }
    notify() {
        this.deps.forEach(dep => {
            dep.update();
        })
    }
}
class Watcher {
    constructor(vm, cb) {
        this.vm = vm;
        this.cb = cb;
        Dep.target = this;
        this.vm.$data['word'];
        Dep.target = null;
    }
    update() {
        this.cb.call(this.vm, this.vm.$data['word']);
    }
}
class Compile {
    constructor(vm) {
        this.vm = vm;
        this.changeInputValue(vm);
    }
    changeInputValue(vm) {
        let inputs = document.querySelectorAll('input');
        Array.from(inputs).forEach(input => {
            this.update(input,vm);
            input.addEventListener('input', (e) => {
                vm.$data['word'] = e.target.value;
            }, false)
        })
    }
    update(input,vm) {
        input.value = vm.$data['word'];
        new Watcher(vm, function (value) {
            input.value = value;
        })
    }
}