Vue implements three-level navigation display and hiding

<template>
  <div id="app">
    <img alt="Vue logo" src="./assets/logo.png" />
    <HelloWorld msg="Welcome to Your Vue.js App" />
    <div class="first" v-for="(item, key) in navLists" :key="key">
      <li>
        <span @click="handleClick(key)"> {{ item.title }}</span>
        <div
          v-for="(item2, key2) in item.child"
          :key="key2"
          class="second"
          v-show="show2 && currIndex == key"
        >
          <p @click="secondClick(key2)">{{ item2.subTitle }}</p>
          <div
            v-for="(item3, key3) in item2.threeChild"
            :key="key3"
            class="three"
           v-show="show3 && currIndex2 == key2"
          >
            {{ item3.threeTitle }}
          </div>
        </div>
      </li>
    </div>
  </div>
</template>
 
<script>
import HelloWorld from "./components/HelloWorld.vue";
 
export default {
  name: "App",
  components:
    HelloWorld,
  },
  data() {
    return {
      i: 0,
 
      show3: false,
      show2: false,
      navLists: [
        {
          title: "Project Information",
          child: [
            {
              subTitle: "Project Introduction",
              esubTitle: "#projectIntroduction",
              threeChild: [
                { threeTitle: "Three-level navigation" },
                { threeTitle: "Three-level navigation" },
                { threeTitle: "Three-level navigation" },
              ],
            },
            {
              subTitle: "Sample Information",
              threeChild: [
                { threeTitle: "Third level navigation 22" },
                { threeTitle: "Third level navigation 22" },
                { threeTitle: "Third level navigation 22" },
              ],
            },
 
            {
              subTitle: "Sample Information",
              threeChild: [
                { threeTitle: "Third level navigation 33" },
                { threeTitle: "Third level navigation 33" },
                { threeTitle: "Third level navigation 33" },
              ],
            },
          ],
        },
        {
          title: "Project Information 2",
          child: [
            {
              subTitle: "Project Introduction 22",
              threeChild: [
                { threeTitle: "Three-level navigation 44" },
                { threeTitle: "Level 3 Guide 44" },
                { threeTitle: "Third level navigation 22" },
              ],
            },
            {
              subTitle: "Sample Information 22",
            },
          ],
        },
        {
          title: "Project Information 3",
          eTitle: "#projectMessage",
          child: [
            {
              subTitle: "Project Introduction 33",
              esubTitle: "#projectIntroduction",
            },
            {
              subTitle: "Sample Information 33",
              esubTitle: "#sampleInformation",
            },
          ],
        },
        {
          title: "Project Information 2",
          child: [
            {
              subTitle: "Project Introduction 22",
            },
            {
              subTitle: "Sample Information 22",
            },
          ],
        },
        {
          title: "Project Information 3",
          child: [
            {
              subTitle: "Project Introduction 33",
            },
            {
              subTitle: "Sample Information 33",
            },
          ],
        },
      ],
 
      currIndex: "", //Current index spanIndex: [], //Index array arrIndex: "", //Used to determine whether to find the current index by indexing the array. -1 means not found, 0 means found.
 
      currIndex2: "", //Current index of secondary navigation spanIndex2: [], //Index array arrIndex2: "", //Used to determine whether to find the current index by indexing the array. -1 means not found, 0 means found.
    };
  },
  methods: {
    handleClick(index) {
      // Initialize the third-level navigation, which is not displayed by default.
      this.show3 =false;
      this.spanIndex2.splice(-1, 1);
 
      // Current index = index
      this.currIndex = index;
      console.log("current index", index);
      // Determine whether the current index is in the index array spanIndex. There are only two possible values ​​for arrIndex: -1 not found. 0 found.
      this.arrIndex = this.spanIndex.indexOf(index);
      console.log("arrIndex", this.arrIndex);
 
      if (this.arrIndex == 0) {
        //arrIndex == 0, the index is found, delete the index in the index array spanIndex, and hide the secondary navigation.
        this.spanIndex.splice(this.arrIndex, 1);
        this.show2 = false;
      } else {
        // arrIndex ==-1, not found, splice(-1,1) deletes 1 value from the end of the spanIndex array and adds the current index to the index array spanIndex, show2 is true, showing the secondary navigation,
        this.spanIndex.splice(this.arrIndex, 1);
        this.spanIndex.push(index);
        this.show2 = true;
      }
      
      console.log("index array", this.spanIndex);
    },
 
    secondClick(index) {
      console.log(index);
      // Current index = index
      this.currIndex2 = index;
      // Determine whether the current index is in the index array spanIndex. There are only two possible values ​​for arrIndex: -1 not found. 0 found.
      this.arrIndex2 = this.spanIndex2.indexOf(index);
      console.log("arrIndex2", this.arrIndex2);
 
      if (this.arrIndex2 == 0) {
        //arrIndex == 0, the index is found, delete the index in the index array spanIndex, and hide the secondary navigation.
        this.spanIndex2.splice(this.arrIndex2, 1);
        this.show3 = false;
      } else {
        // arrIndex ==-1, not found, splice(-1,1) deletes 1 value from the end of the spanIndex array and adds the current index to the index array spanIndex, show2 is true, showing the secondary navigation,
        this.spanIndex2.splice(this.arrIndex2, 1);
        this.spanIndex2.push(index);
        this.show3 = true;
      }
       console.log("index array 2", this.spanIndex2);
    },
  },
};
</script>
 
<style>
p {
  padding: 5px 0;
  margin-block-start: 0;
  margin-block-end: 0;
}
#app {
  font-family: Avenir, Helvetica, Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-align: center;
  color: #2c3e50;
  margin-top: 60px;
}
.first {
  width: 200px;
  font-size: 24px;
  font-weight: bold;
  /* height: 60px; */
  /* background:red; */
}
.first:hover {
  cursor: pointer;
 
  /* color:red; */
}
.second {
  font-size: 18px;
  font-weight: normal;
  background: #eee;
  margin-left: 50px;
}
.three {
  background: yellow;
  margin-left: 20px;
  font-size: 14px;
}
</style>