Vue 3 Function API - Mixin

PostsPage.vue

<template>
  <div class="container">
    <p v-if="isLoading" class="loading">Posts loading...</p>
    <template v-else>
      <div class="topbar" :class="{ open: pageOffset > 120 }">
        <div class="container content">
          <h3>User #{{ id }} posts</h3>
          <span class="count">{{ count }} items</span>
        </div>
      </div>
      <h1>User #{{ id }} posts</h1>
      <span class="count">{{ count }} items</span>
      <div v-for="post in posts" :key="post.id" class="box">
        <h3>{{ post.title }}</h3>
        <p>{{ post.body }}</p>
      </div>
    </template>
  </div>
</template>

<script>
const scrollMixin = {
  data() {
    return {
      pageOffset: 0
    }
  },
  mounted() {
    window.addEventListener('scroll', this.update)
  },
  destroyed() {
    window.removeEventListener('scroll', this.update)
  },
  methods: {
    update() {
      this.pageOffset = window.pageYOffset
    }
  }
}
export default {
  mixins: [scrollMixin],
  props: {
    id: Number,
    isLoading: Boolean,
    posts: Array,
    count: Number
  }
}
</script>

<style lang="scss" scoped>
.box {
  padding: 0.5em 1.5em;
  margin: 1em 0;
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.05);
  border-radius: 10px;
  background: #fff;
}
.count {
  background: #48d8bb;
  padding: 4px 10px;
  font-size: 14px;
  border-radius: 100px;
  color: #fff;
}
.loading {
  text-align: center;
}
.topbar {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  overflow-y: hidden;
  background: #fff;
  box-shadow: 0 2px 20px rgba(0, 0, 0, 0.1);
  max-height: 0;
  transition: all 0.5s ease-out;
  &.open {
    max-height: 100px;
  }
  .content {
    display: flex;
    align-items: center;
    justify-content: space-between;
  }
}
</style>