Summary of the methods and example usage of vue3 component communication

<child :msg2="msg2" />
<script setup>
    const props = defineProps({
        // Writing method one        msg2:String
        // Write method two        msg2:{
            type:String,
            default:''
        }
    })
    (props) // {msg2:'This is the information of the pass-through subcomponent 2'}</script>

//
<template>
    // Writing method one    <div @click="emit('myclick')">Button</div>
    // Write method two    <div @click="handleClick">Button</div>
</template>
<script setup>
    // Method 1    const emit = defineEmits(['myClick'],['myClick2'])
    // Method 2    const handleClick = () => {
        emit('myClick','This is the message sent to the parent component');
     }
      
     // Method 2 does not apply to vue3.2, the useContext() used has been discarded     import { useContext } from 'vue'
     const { emit } = useContext()
     const handleClick = () => { 
      emit('myClick','This is the message sent to the parent component'   
     }
</script>
 
// Response<template>
    <child @myClick="onMyClick"></child>
</template>
<script setup>
    import child from "./"
    import onMychilk = (msg) => {
        (msg) // Message received by the parent component    }
</script>

<script setup>
    // Method 1: UseContext() has been discarded after vue3.2    import { useContext } from 'vue'
    const ctx = useContext()
    // Exposing the attributes to the outside can be done, etc.    ({
        childName: 'This is the attribute of the subassembly',
        someMethod(){
        ('This is the method of the child component')
        }
    })
</script>
 
// Note ref="comp"<template>
    <child ref="comp"></child>
    <button @click="handleClick">Button</button>
</template>
<script>
    import child from './'
    import { ref } from 'vue' 
    const comp = ref(null)
    const handleClick = () => {
        ()
        () // Call the method of exposing subcomponents to the outside    }
</script>

// Parent component<child :msg1="msg1" :msg2="msg2" title="3333"></child>
<script setup>
    import child from './'
    import { ref,reactive } from 'vue
    const msg1 = ref('111')
    const msg2 = ref('222')
</script>
 
// Subcomponents<script setup>
    import { defineProps,useContext,useAttars } from 'vue'
    const props = defineProps({
        msg1: String
    })
     
    // Method 1    const ctx = useContext()
    () // {msg2:'222',title:'333'}
     
    // Method 2    const attrs = useAttars()
    (attars)  // {msg2:'2222',title:'3333'}
</script>

<child v-model:key="key" v-modle:value="value" />
<script>
    import child from './'
    import { ref,reactive } from 'vue'
    const key = ref('111')
    const value = ref('222')
</script>
 
//Subcomponent<template>
   <button @click="handleClick"></button>
</template>
<script setup>
    // Method 1 v3.2 has been removed    import { useContext } from 'vue'
    const { emit } = useContext()
     
    // Method 2    import { defineEmits } from 'vue'
    const emit = defineEmits(['key','value'])
     
    //usage    const handleClick = () => {
        emit('update:key','New key')
        emit('update:value','New value')
    }
</script>

// Parent component<script setup>
    import { provide } from 'vue'
    const name = provide('name')
    ('name','Mu Hua')
</script>
//Subcomponent<script setup>
    import { inject } from 'vue'
    const name = inject('name')
    (name) //Mu Hua</script>

//store/
import { createStore } from 'vuex'
export default createStore({
    state:{count:1},
    getters:{
        getCount:state=>
    },
    mutations:{
        add(state){
            ++
        }
    }
   })
 // 
 import { createApp } from 'vue'
 import APP from './'
 import store from './store'
 createApp(APP).use(store).mount("#app")
  
 // Use directly <template>
     <div>
         {{ $ }}
     </div>
     <button @click="$('add')">
     </button>
 </template>
  
 // Get <script setup>
     import { useStore,computed } from 'vuex'
     const store = useStore()
     ()
      
     const count = computed (()=>)
     (count)
 </script>

import mitt from 'mitt'
const mitt = mitt()
export default mitt

// Component A<script setup>
    import mitt from './mitt'
    const handleClick = () => {
        ('handleChange')
    }
</script>
// Component B<script setup>
import mitt from './mitt'
import { onUnmounted } from 'vue'
const someMethod = () => {...}
('handleChange',someMethod)
onUnmounted(()=>{
    ('handleChange',someMethod)
})
</script>