js 吸顶效果

通过js监听滚动条事件来实现吸顶效果，该方法接受一个dom参数，返回 一个解绑事件的方法。

export function useCeiling(el) {
    const parentNode = el.parentNode;
    const parentTop = parentNode.offsetTop;
    // 子组件距离父组件顶部的距离
    const childTop = el.offsetTop - parentTop;
    const childLeft = el.offsetLeft - parentNode.offsetLeft;
    parentNode.addEventListener('scroll', bindEvent);
    function bindEvent() {
        if (this.scrollTop >= childTop) {
            el.style.position = 'fixed';
            el.style.top = `${parentTop}px`;
            el.style.left = `${childLeft}px`;
            el.style.zIndex = '9999';
        } else {
            el.style.position = 'static';
        }
    }
    function unBind() {
        parentNode.removeEventListener('scroll', bindEvent);
    }

    return {
        unBind
    }
}

在Vue中使用

<template>
  <div class="frame" ref="frame">
    <div style="height: 600px"></div>
    <div class="child" ref="child"></div>
    <div style="height: 1200px"></div>
  </div>
</template>

<script>
import {useCeiling} from "@/views/js/UseVue";
let unbindObj = {};
export default {
  name: "Ceiling",
  methods: {
    init() {
      unbindObj = useCeiling(this.$refs.child);
    }
  },
  mounted() {
    this.init();
  },
  destroyed() {
    const {unBind} = unbindObj;
    typeof unBind === 'function' && unBind();
  }
}
</script>

<style scoped>
.frame {
  width: 100%;
  height: 500px;
  background-color: #42b983;
  overflow: auto;
  position: relative;

}
.child {
  width: 100%;
  height: 100px;
  background-color: #fff;
}
</style>