摘要：最近在用的后臺模板，從上下載后發現左側導航欄最多支持到二級菜單也發現很多童鞋在問如何實現三級菜單。在實際的應用場景中還是會出現三級菜單的需求的，木有其他好辦法，只能自己手動改代碼了。

最近在用 iview-admin的Vue后臺模板，從git上下載后發現左側導航欄最多支持到二級菜單,也發現很多童鞋在問如何實現三級菜單。在實際的應用場景中還是會出現三級菜單的需求的，木有其他好辦法，只能自己手動改代碼了。

1. 第一步：首先改寫VUE中的模板，修改sidebarMenu.vue文件，文件具體目錄建下圖：

將Menu導航菜單組件的的二級嵌套結構改為三級嵌套，無非就是判斷二級路由頁面下是否有children屬性及是否含有子元素，有的話直接v-for循環生成子元素標簽，新結構如下：

組件中methods下添加一個方法isThirdLeveMenu,判斷是否含有children屬性:

methods: {
    changeMenu(active) {
      this.$emit("on-change", active);
    },
    itemTitle(item) {
      if (typeof item.title === "object") {
        return this.$t(item.title.i18n);
      } else {
        return item.title;
      }
    },
    isThirdLeveMenu(child){
       if(child.children){
           if(child.children.length>0)return true;
           else  return false;
       }
       else {
         return false;
       }
    }
  },

第二步：修改創建當前path路徑的邏輯方法：setCurrentPath ,在libs文件夾下util.js文件中：

util.setCurrentPath = function (vm, name) {
    let title = "";
    let isOtherRouter = false;
    vm.$store.state.app.routers.forEach(item => {
        if (item.children.length === 1) {
            if (item.children[0].name === name) {
                title = util.handleTitle(vm, item);
                if (item.name === "otherRouter") {
                    isOtherRouter = true;
                }
            }
        } else {
            item.children.forEach(child => {
                if (child.name === name) {
                    title = util.handleTitle(vm, child);
                    if (item.name === "otherRouter") {
                        isOtherRouter = true;
                    }
                }
            });
        }
    });
    let currentPathArr = [];
    //去首頁
    if (name === "home_index") {
        currentPathArr = [
            {
                title: util.handleTitle(vm, util.getRouterObjByName(vm.$store.state.app.routers, "home_index")),
                path: "",
                name: "home_index"
            }
        ];
    } 
    //去導航菜單一級頁面或者OtherRouter路由中的頁面
    else if ((name.indexOf("_index") >= 0 || isOtherRouter) && name !== "home_index") {
        currentPathArr = [
            {
                title: util.handleTitle(vm, util.getRouterObjByName(vm.$store.state.app.routers, "home_index")),
                path: "/home",
                name: "home_index"
            },
            {
                title: title,
                path: "",
                name: name
            }
        ];
    } 
    //去導航菜單二級頁面或三級頁面
    else {
        let currentPathObj = vm.$store.state.app.routers.filter(item => {

            var hasMenu;
            if (item.children.length <= 1) {
                hasMenu = item.children[0].name === name;
                return hasMenu;
            } else {
                let i = 0;
                let childArr = item.children;
                let len = childArr.length;
                while (i < len) {
                    //如果是三級頁面按鈕，則在二級按鈕數組中找不到這個按鈕名稱
                    //需要二級頁面下可能出現三級子菜單的情況邏輯加入
                    if (childArr[i].name === name) {
                        hasMenu = true;
                        return hasMenu;
                    }
                    i++;
                }
                //如果一級，二級菜單下都沒有此按鈕名稱，則遍歷三級菜單
                if(!hasMenu){
                    for(let m=0;m {
                return  child.name === name;
            })[0];

           // let thirdLevelObj =
           console.log(childObj)
           //二級頁面
            if (childObj) {
                currentPathArr = [
                    {
                        title: "首頁",
                        path: "/home",
                        name: "home_index"
                    },
                    {
                        title: currentPathObj.title,
                        path: "",
                        name: currentPathObj.name
                    },
                    {
                        title: childObj.title,
                        path: currentPathObj.path + "/" + childObj.path,
                        name: name
                    }
                ];
            }
            //childobj為undefined，再從三級頁面中遍歷
            else {
                let thirdObj;
                let childObj = currentPathObj.children.filter((child) => {
                    let hasChildren;
                    hasChildren = child.name === name;
                    if (hasChildren) return hasChildren

                    if (child.children) {
                        let sonArr = child.children;
                        for (let n = 0; n < sonArr.length; n++) {
                            if (sonArr[n].name === name) {
                                thirdObj = sonArr[n];
                                hasChildren = true;
                                return hasChildren;
                            }
                        }
                    }
                    return hasChildren
                })[0];

                if(thirdObj && childObj){
                    currentPathArr = [
                        {
                            title: "首頁",
                            path: "/home",
                            name: "home_index"
                        },
                        {
                            title: currentPathObj.title,
                            path: "",
                            name: currentPathObj.name
                        },
                        {
                            title: childObj.title,
                            path: "",               //設為空是因為此二級菜單沒有實際頁面且用于面包屑組件顯示，path為空的將不可單擊
                            name: childObj.name
                        },
                        {
                            title: thirdObj.title,
                            path: currentPathObj.path + "/" + childObj.path + "/" + thirdObj.path,
                            name: thirdObj.name
                        }
                    ];
                }
                
            }
            
        }
    }
    
    vm.$store.commit("setCurrentPath", currentPathArr);
    return currentPathArr;
};

第三步：建立三級頁面test-child.vue,testcaca.vue和三級路由的容器組件artical-publish-center.vue
artical-publish-center.vue結構如下圖： 要有標簽

其他兩個三級頁面vue隨便寫了：

第四步：到這里，容器可以實現期待已久三級菜單了，^_^. 在router里添加三級頁面路由，router文件夾下router.js中：
加到appRouter中吧,可以放到title: "組件"的children數組中：

{
                path: "artical-publish",
                title: "用戶配置",
                name: "artical-publish",
                icon: "compose",
                component: () => import("@/views/test/artical-publish-center.vue"), //引用三級頁面的中間容器層
                children:[
                    {
                        path: "testcaca",
                        icon: "ios-pause",
                        name: "testcaca",
                        title: "test4",
                        component: () => import("@/views/test/testcaca.vue")
                    },
                    {
                        path: "test-child",
                        icon: "ios-pause",
                        name: "test-child",
                        title: "test-child",
                        component: () => import("@/views/test/test-child.vue")
                    }
                ]
            }  

最后保存，運行你的項目，看下三級菜單出來了吧：