Element中的Cascader（级联列表）动态加载省\市\区数据的方法

var c={name: 'bob'}
var d=c
d.name = 'tom'
console.log(c)
// {name: "tom"}

var a = [
 {
  value: '2',
  children: [
   {
    value: '2-1',
    children: [
     {
      value: '2-1-1',
      children: [],
     },
    ],
   },
   {
    value: '2-2',
    children: [
     {
      value: '2-2-1',
      children: [],
     },
     {
      value: '2-2-2',
      children: [
       {
        value: '2-2-2-1',
        children: [],
       },
      ],
     },
    ],
   },
  ],
 },
]
var b = ['2','2-2','2-2-1']

a[0].children[1].children[0]

{
  value: '2-2-1',
  children: [],
 },

a[0].children[1].children[0].children = [{value: '2-2-1-1',children: []}]

console.log(a)

findRegionOption(regionOptions, regionArr) {
   if (_.isEmpty(regionArr) || _.isEmpty(regionOptions)) {
    return null
   }

   let regionId = _.first(regionArr)
   let regionOption = _.find(regionOptions, regionOption => {
    return regionOption.value === regionId
   })
   
   if (!regionOption) {
    return null
   }
   
   let tailRegionArr = _.tail(regionArr) // lodash的tail方法，获取除了array数组第一个元素以外的全部元素。

   if (_.isEmpty(tailRegionArr)) {
    return regionOption
   }
   return this.findRegionOption(regionOption.children, tailRegionArr)
}

loadRegionChild(regionIdArr) {
 let regionOptions = this.regionHiera
 let regionOptionInUI = this.findRegionOption(regionOptions, regionIdArr)
 if (
  !regionOptionInUI ||
  !regionOptionInUI.children ||
  regionOptionInUI.children.length > 0
 ) {
  return null
 }

 let regionKey = _.last(regionIdArr)
 if (!regionKey) {
  return null
 }

 api
  .getRegionHiera(regionKey)
  .then(res => {
   let regionHiera = res.data
   regionOptionInUI.children = regionChildrenTransfomed // 动态加载赋值
  })
}

<template>
 <div>
   <el-cascader :options="regionHiera" v-model="selectedRegion" change-on-select/>
 </div>
</template>

<script>
export default {
 name: 'Test',
 data() {
  return {
   selectedRegion: [],
   regionHiera: [
    { label: 'Malaysia', value: '136', children: [] },
    { label: 'Indonesia', value: '106', children: [] },
    { label: '中华人民共和国', value: '100000', children: [] },
    { label: 'United States', value: '244', children: [] },
   ],
  }
 },
 watch: {
  selectedRegion(nv) {
   this.loadRegionChild(nv)
  },
 },
  methods: {
   findRegionOption(regionOptions, regionArr) {
   if (_.isEmpty(regionArr) || _.isEmpty(regionOptions)) {
    return null
   }

   let regionId = _.first(regionArr)
   let regionOption = _.find(regionOptions, regionOption => {
    return regionOption.value === regionId
   })
   if (!regionOption) {
    return null
   }
   let tailRegionArr = _.tail(regionArr)
   if (_.isEmpty(tailRegionArr)) {
    return regionOption
   }
   return this.findRegionOption(regionOption.children, tailRegionArr)
  },
  loadRegionChild(regionIdArr) {
   let regionOptions = this.regionHiera
   let regionOptionInUI = this.findRegionOption(regionOptions, regionIdArr)
   if (
    !regionOptionInUI ||
    !regionOptionInUI.children ||
    regionOptionInUI.children.length > 0
   ) {
    return null
   }

   let regionKey = _.last(regionIdArr)
   if (!regionKey) {
    return null
   }

   api
    .getRegionHiera(regionKey)
    .then(res => {
     let regionHiera = res.data //后台返回数据
     regionOptionInUI.children = regionChildrenTransfomed
    })
  },
  }
}
</script>