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Here you can Sed posuere consectetur est at lobortis. Donec ullamcorper nulla non metus auctor fringilla. Maecenas sed diam eget risus varius blandit sit amet non magna. Donec id elit non mi porta gravida at eget metus. Praesent commodo cursus magna, vel scelerisque nisl consectetur et.

HTML

            
              <div id="app">
  {{obj}}
  <button @click="add">修改对象的count属性触发watch</button>
  <button @click="addPrototype">修改对象的a属性触发watch</button>
</div>
            
          
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CSS

            
              
            
          
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JS

            
              const vm = new Vue({
  el: "#app",
  data: {
    obj: {
      count: 0,
      a: "默认",
      c:{
        a: 1
      }
    },
    step: 1
  },
  created:()=>{ // 箭头函数问题 this指向undefined
   console.log('lala',this.obj) 
  },
  watch: {
    obj:{
      handler(val, oldVal){
        console.log("啦啦啦", this.obj, val, oldVal);
      },
      deep: true,
      immediate: true
    },
    step: {
      //watch
      handler(val, oldVal) {
        console.log("默认触发一次", val, oldVal);
      },
      immediate: true
    }
  },
  methods: {
    add() {
      this.obj.count = this.obj.count + this.step;
      this.step += 1;
    },
    addPrototype() {
      this.obj.c.a++; // 支持多层属性监听
      // this.obj.a = this.obj.count; 
      // this.obj.c= this.obj.count;
      //  如果把上面第一行注释,第二行取消注释
      // 那么将不会触发深度watch因为自己添加的属性里面没有get set方法 c属性不会被监听         
    }
  }
});

            
          
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999px

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