场景：

项目信息中，总项目需要获取子项目的所有备注信息进行汇总

JS写法：

let vm = document.getElementsByName("online-form")[0].__vue__;
//子表
vm.$watch('data.jzbzfzdzbzd.sub_zbzdzfz',function(newVal,oldVal){  
    let arraya = data.jzbzfzdzbzd.sub_zbzdzfz;
    if(arraya && arraya.length>0){
  let sy = "";
      for(var i=0;i<arraya.length;i++){
if(""!=data.jzbzfzdzbzd.sub_zbzdzfz[i].xmbz){
if(i!=0){
sy+="，";
}
sy+=data.jzbzfzdzbzd.sub_zbzdzfz[i].xmbz;
}
      }
  data.jzbzfzdzbzd.xmbz = sy;
    }
},{ deep:true});   

demo数据结构参考：

{
    "jzbzfzdzbzd": {
        "xmbz": "编号：12544，编号：13258",
        "xmm": "矿产集团管理平台搭建总项目",
        "xmjl": "",
        "sub_zbzdzfz": [
            {
                "xmmc": "山西分部项目",
                "xmbz": "编号：12544",
                "xmjl": "",
                "sub_guid": "8e9e5638-7c97-42dc-ad40-718979f470fb"
            },
            {
                "xmmc": "邢台分部项目",
                "xmbz": "编号：13258",
                "xmjl": "",
                "sub_guid": "5b59704a-db31-4300-ba63-7ddfe6658fb6"
            }
        ],
        "initData": {
            "zbzdzfz": {
                "xmmc": null,
                "xmbz": null,
                "xmjl": null
            }
        }
    }
}

补充其他写法：

let vm = document.getElementsByName("online-form")[0].__vue__;
vm.$watch('data.ccsqmx.sub_ccsqjtmxb', (newVal, oldVal) => {
        handleJoinGwcode(newVal);
  	handleJoinJplx(newVal);
    }, {
        immediate: true,
        deep: true
    })
function handleJoinGwcode(newVal) {
    vm.data.ccsqmx.txrdwb = newVal.map(item => {
        return item.gwcode
    }).join(",")
}
function handleJoinJplx(newVal){
		vm.data.ccsqmx.gnwjpdwb = newVal.map(item => {
        return item.jtlb//子表字段别名
    }).unique().join(",")//汇总信息并过滤重复内容
}

let vm = document.getElementsByName("online-form")[0].__vue__;
vm.$watch('data.bxdj.sub_clf', (newVal, oldVal) => {
        handleJoinjpiao(newVal);//机票
  			handleJoinchechuanpiao(newVal);//车船费
  			handleJoinshineijiaotong(newVal);//市内交通
  			handleJoinzhusufei(newVal);//住宿费
  			handleJoinchuchaibutie(newVal);//出差补贴
  			handleJoinqita(newVal);//其他
    }, {
        immediate: true,
        deep: true
    })
//机票
function handleJoinjpiao(newVal) {
  //debugger
  let sum = 0
    newVal.forEach(item => {
      if(item.fylx == '1'){
      sum += item.zfy
      }
    })
  vm.data.bxdj.F_jpf = sum
}
//车船费
function handleJoinchechuanpiao(newVal) {
  //debugger
  let sum = 0
    newVal.forEach(item => {
      if(item.fylx == '4'||item.fylx == '2'||item.fylx == '3'||item.fylx == '9'||item.fylx == '10'){
      sum += item.zfy
      }
    })
  vm.data.bxdj.F_ccf = sum
}
//市内交通
function handleJoinshineijiaotong(newVal) {
  //debugger
  let sum = 0
    newVal.forEach(item => {
      if(item.fylx == '5'){
      sum += item.zfy
      }
    })
  vm.data.bxdj.F_snjtf = sum
}
//住宿费
function handleJoinzhusufei(newVal) {
  //debugger
  let sum = 0
    newVal.forEach(item => {
      if(item.fylx == '6'||item.fylx == '7'){
      sum += item.zfy
      }
    })
  vm.data.bxdj.F_zsf = sum
}
//出差补贴
function handleJoinchuchaibutie(newVal) {
  //debugger
  let sum = 0
    newVal.forEach(item => {
      if(item.fylx == '8'){
      sum += item.zfy
      }
    })
  vm.data.bxdj.F_ccbz = sum
}
//其他
function handleJoinqita(newVal) {
  //debugger
  let sum = 0
    newVal.forEach(item => {
      if(item.fylx == '11'){
      sum += item.zfy
      }
    })
  vm.data.bxdj.F_qt = sum
}