详解Vue3中Watch监听事件的使用

watch(WatcherSource, Callback, [WatchOptions])

type WatcherSource<T> = Ref<T> | (() => T)

interface WatchOptions extends WatchEffectOptions {

--     deep?: boolean  ``// 默认：false`

--     immediate?: boolean  ``// 默认：false`
}

import { watch } from 'vue'

setup(props){
         const state = reactive({ 
           count: 0 ,
           message:'Hellow world'
         });
         watch(state,()=>{
            console.log(state.count); --单个监听
         })
         return {
           state,
         }
},

<template>
 <div>
   age: {{obj1.age}}

   name: {{obj.name}}
   

   list:
   <ul>
     <li v-for="(item, index) in obj.list" :key="index"> {{item}} </li>
   </ul>
   <hr>
   <button @click="changeName">改变name</button>
   <button @click="changeList">改变list</button>
   <button @click="changeAge">改变age</button>
 </div>
</template>
<script lang="ts">
import {defineComponent, reactive, watch} from 'vue';
export default defineComponent({
 setup () {
   let obj = reactive({
     name: '1111',
     list: ['222', '222222', '222222']
   })
   let obj1 = reactive({
     age: 18
   })
   function changeName () {
     obj.name += '+'
   }

   function changeList () {
     obj.list[0] += '+'
   }

   function changeAge () {
     obj1.age++
   }

   watch([obj, obj1], () => {
     console.log(obj.name)
     if(obj.age>28){
         watchFunc()  // 停止监听`
     }
   }, {
     // 页面加载会先执行一次
     immediate: true
   })

   return {
     obj,
     changeName,
     changeList,
     changeAge,
     obj1
   }
 }
})
</script>
<style scoped>
</style>

<template>
  <div class="watch-test">
    <div>ref定义数组：{{arrayRef}}</div>
    <div>reactive定义数组：{{arrayReactive}}</div>
  </div>
  <div>
    <button @click="changeArrayRef">改变ref定义数组第一项</button>
    <button @click="changeArrayReactive">改变reactive定义数组第一项</button>
  </div>
</template>

<script>
  import {ref, reactive, watch} from 'vue'

  export default {
    name: 'WatchTest',
    setup() {
      const arrayRef = ref([1, 2, 3, 4])
      const arrayReactive = reactive([1, 2, 3, 4])

      //ref not deep
      const arrayRefWatch = watch(arrayRef, (newValue, oldValue) => {
        console.log('newArrayRefWatch', newValue, 'oldArrayRefWatch', oldValue)
      })

      //ref deep
      const arrayRefDeepWatch = watch(arrayRef, (newValue, oldValue) => {
        console.log('newArrayRefDeepWatch', newValue, 'oldArrayRefDeepWatch', oldValue)
      }, {deep: true})

      //reactive，源不是函数
      const arrayReactiveWatch = watch(arrayReactive, (newValue, oldValue) => {
        console.log('newArrayReactiveWatch', newValue, 'oldArrayReactiveWatch', oldValue)
      })

      // 数组监听的最佳实践- reactive且源采用函数式返回，返回拷贝后的数据
      const arrayReactiveFuncWatch = watch(() => [...arrayReactive], (newValue, oldValue) => {
        console.log('newArrayReactiveFuncWatch', newValue, 'oldArrayReactiveFuncWatch', oldValue)
      })

      const changeArrayRef = () => {
        arrayRef.value[0] = 6
      }
      const changeArrayReactive = () => {
        arrayReactive[0] = 6
      }
      return {
        arrayRef,
        arrayReactive,
        changeArrayRef,
        changeArrayReactive
      }
    }
  }
</script>

<template>
  <div class="watch-test">
    <div>user:{</div>
      <div>name:{{objReactive.user.name}}</div>
      <div>age:{{objReactive.user.age}}</div>
    <div>}</div>
    <div>brand:{{objReactive.brand}}</div>
    <div>
      <button @click="changeAge">改变年龄</button>
    </div>
  </div>
</template>

<script>
  import {ref, reactive, watch} from 'vue'
  import _ from 'lodash';

  export default {
    name: 'WatchTest',
    setup() {
      const objReactive = reactive({user: {name: '小松菜奈', age: '20'}, brand: 'Channel'})

      //reactive 源是函数
      const objReactiveWatch = watch(() => objReactive, (newValue, oldValue) => {
        console.log('objReactiveWatch')
        console.log('new:',JSON.stringify(newValue))
        console.log('old:',JSON.stringify(oldValue))
      })

      //reactive，源是函数，deep：true
      const objReactiveDeepWatch = watch(() => objReactive, (newValue, oldValue) => {
        console.log('objReactiveDeepWatch')
        console.log('new:',JSON.stringify(newValue))
        console.log('old:',JSON.stringify(oldValue))
      }, {deep: true})

      // 对象深度监听的最佳实践- reactive且源采用函数式返回，返回深拷贝后的数据
      const objReactiveCloneDeepWatch = watch(() => _.cloneDeep(objReactive), (newValue, oldValue) => {
        console.log('objReactiveCloneDeepWatch')
        console.log('new:',JSON.stringify(newValue))
        console.log('old:',JSON.stringify(oldValue))
      })

      const changeAge = () => {
        objReactive.user.age = 26
      }

      return {
        objReactive,
        changeAge
      }
    }
  }
</script>