sync修饰符

常规情况下，我们进行子向父更新值得时候都需要这样做

<template>
  <div id="app">
    <hello-world :value="value" @change="changeValue"></hello-world>
  </div>
</template>

<script>
import HelloWorld from './components/HelloWorld.vue'

export default {
  name: 'App',  //父组件
  components: {
    HelloWorld,
  },
  data(){
    return{
      value:''
    }
  },
  methods:{
    changeValue(e){
      this.value = e
    } 
  }
}
</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>

<template>
  <div class="hello">
   <input
      placeholder="placeholder"
      v-bind:value="value"
    >
    <br>
    <button @click="change">change</button>
  </div>
</template>

<script>
export default {
  name: 'HelloWorld',
  props: ['value'],
  data(){
    return {

    }
  },
  methods:{
    change(){
      this.$emit('change', '常规子向父更新值')
    }
  }
}
</script>

<style scoped>

</style>

使用sync修饰符实现子向父更新值

<template>
  <div id="app">
    <hello-world :value.sync="value"></hello-world>
  </div>
</template>

<script>
import HelloWorld from './components/HelloWorld.vue'

export default {
  name: 'App',  //父组件
  components: {
    HelloWorld,
  },
  data(){
    return{
      value:''
    }
  },
  methods:{
    
  }
}
</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>

<template>
  <div class="hello">
   <input
      placeholder="placeholder"
      v-bind:value="value"
    >
    <br>
    <button @click="change">change</button>
  </div>
</template>

<script>
export default {
  name: 'HelloWorld',
  props: ['value'],
  data(){
    return {

    }
  },
  methods:{
    change(){
      this.$emit('update:value','我是由vue修饰符.sync改变的')
    }
  }
}
</script>

<style scoped>

</style>