24 - 激活的样式-指令

[webfanrc]

<script setup lang='ts'>

import { ref, watchEffect, watch } from "vue"

/**
 * Implement the custom directive
 * Make sure the list item text color changes to red when the `toggleTab` is toggled
 *
*/
const VActiveStyle = {
  mounted(el, { value }) {
    const [style, condition] = value
    watchEffect(() => {
      if (condition?.()) { // 可选链操作符，if true
        // 用于返回一个给定对象自身可枚举属性的键值对数组
        Object.entries(style).forEach(([key, value])=> {
          el.style[key] = value
        })
      } else {
        Object.keys(style).forEach(key => {
          el.style[key] = ''
        })
      }
    })
  },
}

const list = [1, 2, 3, 4, 5, 6, 7, 8]
const activeTab = ref(0)
function toggleTab(index: number) {
  activeTab.value = index
}

</script>

<template>
  <ul>
    <li
      v-for="(item,index) in list"
      :key="index"
      v-active-style="[{'color':'red'},() => activeTab === index]"
      @click="toggleTab(index)"
    >
      {{ item }}
    </li>
  </ul>
  {{activeTab}}
</template>