009. 样式文件的作用域

App.vue
----------------------------------------
<template >
  <div id="app">
    <h2>Hello World</h2>
    <HelloWorld />
  </div>
</template>

<script>
import HelloWorld from "./HelloWorld.vue";
export default {
  components: {
    HelloWorld
  }
}
</script>

<style scoped>
  h2{
    color: red;
  }
</style>

HelloWorld.vue
<template >
  <div id="app">
    <h2>Hello World</h2>
    <HelloWorld />
  </div>
</template>

<script>
import HelloWorld from "./HelloWorld.vue";
export default {
  components: {
    HelloWorld
  }
}
</script>

<style scoped>
  h2{
    color: red;
  }
</style>

#  如果 style 加上了scoped 属性 即标识只对本组件生效