<router-link :to="{path:'/b/'+id,query:{breadNum:2}}"></router-link>

<router-link :to="{path:'/bbdetail/'+id,query:{breadNum:3}}"></router-link>

<template>
  <div class="breadbox">
   <span v-for="(item,index) in breadlist" >
    <router-link :to="item.path">{{item.name}}</router-link>
   </span>
  </div>
</template>
<script>
 export default{
  created() {
   this.getBreadcrumb();
  },
  data() {
   return {
    breadlist: '' // 路由集合
   }
  },
  methods: {
   getBreadcrumb() {
    var breadNumber= this.$route.query.breadNum || 1;//url变量breadNum记录层级，默认为1，如果大于1，要添加上变量；
    var breadLength=this.$store.state.breadListState.length;//目前breadlist集合数组个数
    var curName=this.$route.name;
    var curPath=this.$route.fullPath;
    var newBread={name:curName,path:curPath};
    var ishome=curName=='首页';
    console.log(ishome);
    if(breadNumber===1){//点击一级菜单
     this.$store.commit('breadListStateRemove',1);//初始化，只有首页面包屑按钮
     if(!ishome)//如果不是首页
      this.$store.commit('breadListStateAdd',newBread);//当前页面添加到breadlist集合
    }
    else if(breadLength<=breadNumber){//如果不是一级导航，并且breadlist集合个数等于或者小于目前层级
     this.$store.commit('breadListStateAdd',newBread);//要把当前路由添加到breadlist集合
    }else{
     this.$store.commit('breadListStateRemove',parseInt(breadNumber)+1);//如果往回点面包屑导航，截取；
    }
    this.breadlist=this.$store.state.breadListState;
    console.log(this.breadlist);
   }
  },
  watch: {
   $route () {
    this.getBreadcrumb();
   }
  },
 }
</script>

export default store = new Vuex.Store({
 state: {
 breadListState:[
  {name:'首页',path:'/'}
 ]
 },
 mutations: {
 breadListStateAdd(state,obj){
  state.breadListState.push(obj);
 },
 breadListStateRemove(state,num){
  state.breadListState=state.breadListState.slice(0,num);
 }
 }

})

{
 path: '/',
 name: '首页',
 component: Main,
 redirect:'/home',
 children:[
  {path: '/a',name: 'A页面',component: APage},
  {path: '/b/:id',name: 'B页面',component: BPage},
  {path: '/bdetail/:id',name: 'C页面',component: CPage},
 ]
}