vue3实现v-model原理详解

const target = {
 a: 1
}
const handers = {
 get() {
  // 当对 observed.a 进行取值时会触发
 },
 set() {
  // 当对 observed.a 进行赋值时会触发
 },
 // 还有一些额外的参数如 has 等，这里用不到，就不多说了
 ....
}
const observed = new Proxy(target, handers)

const target = {
 a: {
  b: 1
 }
}

...

const observed = new Proxy(target, handers)

const target = {
 a: {
  b: 1
 }
}

function reactive(data: any) {
 const handers = {
  get(target, key, receiver) {
   const res = Reflect.get(target, key, receiver);
   if (isObject(res)) {
    data[key] = reactive(res);
   }
   return target[key];
  }
 }
 const observed = new Proxy(target, handers)
}

const rawToReactive: WeakMap<any, any> = new WeakMap();
const reactiveToRaw: WeakMap<any, any> = new WeakMap();

function reactive(data: any) {
 // 已经有代理
 let observed = rawToReactive.get(data);
 if (observed !== void 0) {
  return observed;
 }
 // 这个数据已经是代理
 if (reactiveToRaw.has(data)) {
  return data;
 }
 const handler = {
  get: function(target: any, key: string, receiver: any) {
   const res = Reflect.get(target, key, receiver);
   if (isObject(res)) {
    data[key] = data[key] = reactive(res);
   }
   return target[key];
  },
  set: function(target: any, key: string, value: any) {
   // 将新值赋值
   target[key] = value;
   // 通知所有订阅者触发更新
   trigger(target);
   // 严格模式下需要设置返回值，否则会报错
   return value;
  }
 };
 // 返回代理监听对象
 observed = new Proxy(data, handler as any);
 rawToReactive.set(data, observed);
 reactiveToRaw.set(observed, data);

 return observed;
}

// 收集watcher依赖
const Dep: Dep = {
 deps: [],
 add(watcher: Watcher) {
  this.deps.push(watcher);
 }
};

// observer跟compile的桥梁，在编译时添加watcher，在数据更新时触发update更新视图
function _watcher(node: any, attr: string, data: any, key: string): Watcher {
 return {
  node,
  attr,
  data,
  key,
  update() {
   // 逐层取值
   const mutationKeys = this.key.split('.');
   if (mutationKeys.length > 1) {
    let d: any = null;
    mutationKeys.forEach(key => (d = this.data[key] || (d && d[key])));
    this.node[this.attr] = d;
    return;
   }
   this.node[this.attr] = this.data[this.key];
  }
 };
}

// 编译模板
function _compile(nodes: any, $data: any) {
 [...nodes].forEach((e, index) => {
  const theNode = nodes[index];
  // 获取到 input标签下的 v-model 属性，并添加watcher
  if (theNode.tagName === 'INPUT' && theNode.hasAttribute('v-model')) {
   const key = theNode.getAttribute('v-model');
   Dep.add(_watcher(theNode, 'value', $data, key));
   // 监听input事件
   theNode.addEventListener('input', () => {
    const mutationKeys = key.split('.');
    if (mutationKeys.length > 1) {
     eval(`$data.${key}='${theNode.value}'`);
     return;
    }
    $data[key] = theNode.value;
   });
  }
  // 获取 v-bind 属性，并添加watcher
  if (theNode.hasAttribute('v-bind')) {
   const key = theNode.getAttribute('v-bind');
   Dep.add(_watcher(theNode, 'innerHTML', $data, key));
  }
 });
 trigger($data);
}

function trigger(target: any, key"my-app" 元素内实现双向绑定



<div id="my-app">
 <h1 v-bind="a"></h1>
 <input v-model="a" type="text">
</div>


vue3 中 new Vue 已经被 createApp 所代替，reactive 是反应原理，可以抽出来单独使用，vue3 外漏了所有内部的 api，都可以在外部使用


const { createApp, reactive } = require('./vue.ts').default;
const App = {
 setup() {
  const react = reactive({
   a: {
    b: {
     c: {
      d: {
       e: 111
      }
     }
    }
   }
  });
  // 测试异步反应
  setTimeout(() => {
   react.a.b.c.d.e = 222;
  }, 100);
  return react;
 }
};
createApp().mount(App, '#my-app');



以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。