vue3.0实现下拉菜单的封装

vue3.0出来已经有段时间的了，也与必要开始研究它了！

先看下我们要实现的效果

很常见的展开显示菜单项的内容，在vue3.0里面怎么开发，这里样式我们用的是bootstrap的默认样式

思路一:

<dropdown :title="'退出'" :list="menulists" />

思路二:

<drop-down :title="'退出'">
   <drop-dowm-item>新建文章</drop-down-item>
   <drop-dowm-item>编辑文章</drop-down-item>
   <drop-dowm-item>个人信息</drop-down-item>
</drop-down>

两种思路都行，相比较而言，第二种思路比较清晰，使用的时候知道具体的层次，也是elementui组件开发的模式.
现在就第二种组件开发思路进行分析

dropdown.ts

<template>
  <div class="dropdown" ref="dropdownref">
    <a
      @click.prevent="toggleopen"
      class="btn btn-secondary dropdown-toggle"
      href="#" rel="external nofollow" 
    >
      {{ title }}
    </a>
    <div class="dropdown-menu" :style="{ display: 'block' }" v-show="isopen">
      <slot></slot>
    </div>
  </div>
</template>

js部分

<script lang="ts">
import { definecomponent, ref, onmounted, onunmounted, watch } from "vue";
import useclickoutside from "../hooks/useclickoutside";
export default definecomponent({
  name: "dropdown",
  props: {
    title: {
      type: string,
      required: true,
    },
  },

  setup(context) {
    const isopen = ref(false);
    //vue3.0获取dom对象的引用
    const dropdownref = ref<null | htmlelement>(null);
    const toggleopen = () => {
      isopen.value = !isopen.value;
    };
    const handleclick = (e: mouseevent) => {
      console.log(e.target, "e");
      if (dropdownref.value) {
        console.log(dropdownref.value);
        if (
        //contains判断节点是否包含节点
          !dropdownref.value.contains(e.target as htmlelement) &&
          isopen.value
        ) {
          isopen.value = false;
        }
      }
    };
    onmounted(() => {
    //注册全局的点击事件
      document.addeventlistener("click", handleclick);
    });
    onunmounted(() => {
    //解绑
      document.removeeventlistener("click", handleclick);
    }); 
    return {
      isopen,
      toggleopen,
      dropdownref,
    };
  },
});
</script>

dropdownitem.ts

<template>
  <li class="dropdowm-option" :class="{ 'is-disabled': disabled }">
    <slot></slot>
  </li>
</template>
<style scoped>

/* 此处是插槽需要穿透 */
.dropdowm-option.is-disabled >>> * {
  color: #6c757d;
  pointer-events: none;
  background-color: transparent;
}
</style>

<script lang="ts">
import { definecomponent } from "vue";

export default definecomponent({
  props: {
    disabled: {
      type: boolean,
      default: false,
    },
  },
  setup() {
    return {};
  },
});
</script>

到这里这个组件就完成了。但是…我们可以看到点击整个document隐藏这个事件与整个组件的关联不大，因此我们可以抽取成一个hooks

useclickoutside.ts

import { ref, onmounted, onunmounted,ref } from 'vue'
const useclickoutside = (elementref:ref<null | htmlelement>) => {
    const isclickoutside = ref(false)
    const handler = (e: mouseevent) => {
        console.log(elementref.value);
        if (elementref.value) {
            if (elementref.value.contains(e.target as htmlelement)) {
                isclickoutside.value = false
            } else {
                isclickoutside.value = true
            }
        }
    }
    onmounted(() => {
      document.addeventlistener("click", handler);
    });
    onunmounted(() => {
      document.removeeventlistener("click", handler);
    });
    return isclickoutside
}

export default useclickoutside

然后再改写我们的dropdown.ts组件

//删掉之前已有的事件逻辑
<script lang="ts">
... 
 const isclickoutside = useclickoutside(dropdownref);
    /* console.log(isclickoutside.value, "isclickoutside"); */
    //引入监听方法，数据变化时我们改变isopen的值为false
    watch(isclickoutside, (newvalue) => {
      if (isopen.value && isclickoutside.value) {
        isopen.value = false;
      }
    });
 ...
</script>

实现了同样的效果，整个组件的代码也精简了不少!

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