3分钟了解vue数据劫持的原理实现

let obj = {
 name: 'jw'
}

/**
* 判断监听的是否是对象
* 如果是对象，就遍历，并且对每个属性进行定义get 和 set
*/

function observer(obj) {
 if(typeof obj === 'object') {
  for (let key in obj) {
  // defineReactive 方法设置get和set，见第三步
   defineReactive(obj, key, obj[key]);
  }
 }
}

function defineReactive(obj, key, value) {
 Object.defineProperty(obj, key, {
  get() {
   return value;
  },
  set(val) {
   console.log('数据更新了')
   value = val;
  }
 })
}

observer(obj);
obj.name = 'haha'

let obj = {
 name: 'jw',
 age: {
  old: 60
 }
}

observer(obj);
obj.age.old = '50'

// 修改defineReactive ， 添加一行代码
function defineReactive(obj, key, value) {
 // 如果对象的属性也是一个对象。迭代处理
 observer(value);
 Object.defineProperty(obj, key, {
  //....
 })
}

observer(obj);
obj.age.old = '50'

obj.skill = [1, 2, 3];
obj.age.push(4);

let arr = ['push', 'slice', 'shift', 'unshift'];
arr.forEach(method=> {
 let oldPush = Array.prototype[method];
 Array.prototype[method] = function(value) {
  console.log('数据更新了')
  oldPush.call(this, value)
 }
})

obj.skill = [1, 2, 3];
obj.skill.push(4);

let obj = {
 name: 'jw',
 age: {
  old: '60'
 }
}

// vue 数据劫持 Observer.defineProperty

function observer(obj) {
 if(typeof obj === 'object') {
  for (let key in obj) {
   defineReactive(obj, key, obj[key]);
  }
 }
}

function defineReactive(obj, key, value) {
 observer(value);

 Object.defineProperty(obj, key, {
  get() {
   return value;
  },
  set(val) {
   console.log('数据更新了')
   value = val;
  }
 })
}
observer(obj);


// obj.age.old = '50'


// Object.defineProperty 对 数组无效
let arr = ['push', 'slice', 'shift', 'unshift'];

arr.forEach(method=> {
 let oldPush = Array.prototype[method];
 Array.prototype[method] = function(value) {
  console.log('数据更新了')
  oldPush.call(this, value)
 }
})
obj.skill = [1, 2, 3];
obj.skill.push(4);