vue3.0 子组件更新父组件的数据

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>lesson 18</title>
  <script src="https://unpkg.com/vue@next"></script>
</head>
<body>
  <div id="root"></div>
</body>
<script>
  const app = Vue.createApp({
    data() {
      return { count: 1 }
    },
    template: `
      <counter v-model="count" />
    `
  });

  app.component('counter', {
    props: ['modelValue'],
    methods: {
      handleClick() {
        this.$emit('update:modelValue', this.modelValue + 3);
      }
    },
    template: `
      <div @click="handleClick">{{modelValue}}</div>
    `
  });

  const vm = app.mount('#root');
</script>
</html>

// 原来的子组件向父组件传递数据需要用 emit 再在父组件用方法接收

// 现在 vue3.0 更新了 v-model