在sapper中更新正文背景颜色

body {
  background-color: red;
}

import { onMount } from 'svelte';

let backgroundColor = 'red';

onMount(() => {
  const button = document.querySelector('button');
  button.addEventListener('click', () => {
    backgroundColor = 'blue';
  });
});

<script>
  import ChildComponent from './ChildComponent.svelte';

  let backgroundColor = 'red';
</script>

<style>
  .parent {
    background-color: {backgroundColor};
  }
</style>

<div class="parent">
  <ChildComponent {backgroundColor} />
</div>