Vue3 setup的注意点及watch监视属性的六种情况分析

  export default {
    name: "Demo",
    beforeCreate(){
      console.log('beforeCreate已执行');
    },
    setup() {
      console.log('setup已执行');
      let person = reactive({
        name: "小明",
        age: 20,
      });
      return {
        person,
      };
    },
  };

  export default {
    name: "Demo",
    props:['msg','age'],
    setup(props) {
      console.log(props);
      let person = reactive({
        name: "小明",
        age: 20,
      });   
      return {
        person,
      };
    },
  };

<template v-slot:qwe>
<span>123</span>
</template>
<template v-slot:ewq>
<span>321</span>
</template>

 console.log(context.slots); // 得到插槽

<Demo @hi="Hello" msg="山鱼" age=10>
</Demo>

  setup() {
    function Hello(){
      console.log('你好！');
    }
    return {
      Hello
    }
  }

 function point(){
        context.emit('hi',666)
      }     
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```js
 function point(){
        context.emit('hi',666)
      }     

import { reactive,computed} from "vue";
  export default {
    name: "Demo",
    setup() {
      let person = reactive({
        firstName: "小",
        lastName: "明",
      }); 
      // 计算属性的简写形式，不考虑修改，是只读的
      /*person.fullName= computed(()=>{
        return person.firstName+'-'+person.lastName
      }) */
      // 计算属性的完整形式（可以读改）
      person.fullName= computed({
        get(){
          return person.firstName +'-'+person.lastName
        },
        set(value){
          const arr = value.split('-')
          person.firstName = arr[0]
          person.lastName = arr[1]
        }
      })
      return {
        person,
      };
    },
  };

    watch(sum, (newvalue, oldvalue) => {
      console.log('当前值为'+newvalue, '以前值为'+oldvalue);
    });

        watch([sum,msg], (newvalue, oldvalue) => {
      console.log('当前值为'+newvalue, '以前值为'+oldvalue);
    });

             watch(person,(newValue, oldValue) => {
                console.log('person变化了',newValue,oldValue)
             })

            watch(()=>person.name,(newValue,oldValue)=>{
               console.log('person.name发生了变化',newValue,oldValue)
           })

watch([()=>{person.age},()=>{person.name}],(newValue,oldValue)=>{
                console.log('person.name发生了变化',newValue,oldValue)
            })

 watch(()=>person.job,(newValue,oldValue)=>{
                console.log('person.name发生了变化',newValue,oldValue)
            }, {deep: true})