Vue3中的 computed,watch,watchEffect的使用方法

<template>
  姓：<input v-model="person.firstName"><br/><br/>
  名：<input  v-model="person.lastName"><br/><br/>
  <span>全名：{{person.fullname}}</span><br/><br/>
  <span>全名：<input v-model="person.fullname"></span>
</template>

<script>
import {Reactive,computed} from 'Vue'
export default {
  name: 'HelloWorld',
  setup(){
    let person = reactive({
      firstName:"张",
      lastName:"三"
    })
    //computed简写形式，没考虑修改
    
    person.fullname = computed({
      get(){
        return person.firstName+"-"+person.lastName;
      },
      set(value){
        const nameArr = value.split('-');
        person.firstName = nameArr[0];
        person.lastName = nameArr[1];
      }
    })
    return{
      person,
    }
  }
}
</script>

<template>
  <h2>当前求和为：{{ sum }}</h2>
  <button @click="sum++">点我sum++</button>
</template>

<script>
import {ref} from 'vue'

export default {
  name: 'Demo',
  watch: {
    
    sum: {
      immediate: true,
      deep:true,
      handler(newValue,oldValue) {
        console.log("sum发生了变化", newValue, oldValue);
      }
    }
  },
  setup() {
    let sum = ref(0);

    return {
      sum,
    }
  }
}
</script>

<template>
  <h2>当前求和为：{{ sum }}</h2>
  <button @click="sum++">点我sum++</button>>
</template>
<script>
import {ref, watch} from 'vue'
export default {
  name: 'Demo',
  setup() {
    let sum = ref(0);
    let msg = ref("你好啊");
    //情况一：监视ref所定义的一个响应式数据
    watch(sum, (newValue, oldValue) => {
      console.log("sum发生了变化", newValue, oldValue);
    })

    return {
      sum
    }
  }
}
</script>

watch(sum, (newValue, oldValue) => {
      console.log("sum发生了变化", newValue, oldValue);
    },{immediate:true})

<template>
  <h2>当前求和为：{{ sum }}</h2>
  <button @click="sum++">点我sum++</button>
  <hr/>
  <h2>信息为：{{ msg }}</h2>
  <button @click="msg+='!'">点我sum++</button>
</template>
<script>
import {ref, watch} from 'vue'
export default {
  name: 'Demo',
  setup() {
    let sum = ref(0);
    let msg = ref("你好啊");

    //情况二：监视ref所定义的多个响应式数据
    watch([sum,msg],(newValue, oldValue) => {
      console.log("sum发生了变化", newValue, oldValue);
    })

    return {
      sum,
      msg
    }
  }
}
</script>

<template>
  <h2>姓名：{{ person.name }}</h2>
  <h2>年龄：{{ person.age }}</h2>
  <h2>薪资：{{ person.job.j1.salary }}K</h2>
  <button @click="person.name+='~'">修改姓名</button>
  <button @click="person.age++">修改年龄</button>
  <button @click="person.job.j1.salary++">涨薪</button>
</template>
<script>
import {reactive, watch} from 'vue'

export default {
  name: 'Demo',
  setup() {
    let person = reactive({
      name: "张三",
      age: 18,
      job:{
        j1:{
          salary:20
        }
      }
    })
    //情况三：监视reactive所定义的一个响应式数据全部属性
    // 1\注意：无法正确获取oldvalue
    // 2\注意：强制开启了深度监视（deep配置无效）
    watch(person, (newValue, oldValue) => {
      console.log("person发生了变化", newValue, oldValue);
    })

    return {
      person
    }
  }
}
</script>

//情况四：监视reactive所定义的一个响应式数据某个属性
    watch(()=>person.name, (newValue, oldValue) => {
      console.log("person的name发生了变化", newValue, oldValue);
    })

//情况五：监视reactive所定义的一个响应式数据某个属性
    watch([()=>person.name,()=>person.age], (newValue, oldValue) => {
      console.log("person的name或age发生了变化", newValue, oldValue);
    })

watch(()=>person.job, (newValue, oldValue) => {
	console.log("person的job发生了变化", newValue, oldValue);
},{deep:true})//由于监视的是reactive对象中的某个属性，deep奏效

	let person = ref({
      name: "张三",
      age: 18,
      job:{
        j1:{
          salary:20
        }
      }
    })
    watch(person.value, (newValue, oldValue) => {
      console.log("person的value发生了变化", newValue, oldValue);
    })
    或
    watch(person, (newValue, oldValue) => {
      console.log("person的value发生了变化", newValue, oldValue);
    },{deep:true})

//watchEffect所指定的回调中用到的数据只要发生变化,则直接重新执行回调
watchEffect(()=>{
	const xl = sum.value
	const x2 = person.age
	console.log( "watchEffect配置的回调执行了")
})

import {reactive,watchEffect} from 'vue'
export default {
  name: 'Demo',
  setup() {
    let person = reactive({
      name: "张三",
      age: 18,
      job:{
        j1:{
          salary:20
        }
      }
    })
    watchEffect(()=>{
      const x1 = person.name;
      console.log("watchEffect所指定的回调执行了"+x1);
    })
    return {
      person
    }
  }
}
</script>

<template>
  姓：<input v-model="person.firstName">
  名：<input  v-model="person.lastName">
  <span>全名：{{fullName}}</span>
  <span>全名：<input v-model="fullName"></span>
</template>
<script lang="ts">
import {defineComponent, reactive, ref,watch,watchEffect} from 'vue';
export default defineComponent({
  setup(){
    let person = reactive({
      firstName:"张",
      lastName:"三"
    });

    const fullName = ref('');

    watch(person,({firstName,lastName})=>{
      fullName.value = firstName+"-"+lastName
    },{immediate:true})

    //不用使用immediate，默认执行一次
    

    watchEffect(()=>{
      const name = fullName.value.split('-');
      person.firstName = name[0];
      person.lastName = name[1];
    })
    return{
      person,
      fullName
    }
  }
});
</script>
<style>
#app {
  font-family: Avenir, Helvetica, Arial, sans-serif;
  -WEBkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-align: center;
  color: #2c3e50;
  margin-top: 60px;
}
</style>