v2&v3 v-model语法糖

<input type="text" v-model="msg" />
<input type="text" :value="msg" @input="msg = $event.target.value" />
或者<input type="text" :value="msg" @input="(e)=>{msg = e.target.value}" />

<child v-model="price"></child>
<child :value="price" @input="(val)=>price=val"></child>
或者<child :value="price" @input="price=$event"></child>

<child :prop.sync="val"></child>
<child :prop="val" @update:prop="val = $event"></child>
或者<child :prop="val" @update:prop="(data)=>{val = data}"></child>
this.$emit('update:prop', newValue)

v-model="count"
:modelValue="count" @update:modelValue="count = $event"

v-model:title="pageTitle"
<ChildComponent :title="pageTitle" @update:title="pageTitle = $event" />