SOURCE

let arrayName = [
    {
        "cityNo": "1516588857",
        "branchNo": "69174749",
        "gridNo": "66614",
        "cityName": "北区",
        "branchName": "郑州",
        "gridName": "郑州中原"
    },
    {
        "cityNo": "1516588857",
        "branchNo": "69174749",
        "gridNo": "66613",
        "cityName": "北区",
        "branchName": "郑州",
        "gridName": "郑州CBD"
    },
    {
        "cityNo": "1516588856",
        "branchNo": "69174690",
        "gridNo": "66340",
        "cityName": "南区",
        "branchName": "武汉",
        "gridName": "武汉楚河汉街"
    },
    {
        "cityNo": "1516588857",
        "branchNo": "69174648",
        "gridNo": "66904",
        "cityName": "北区",
        "branchName": "沈阳",
        "gridName": "沈阳铁西"
    },
    {
        "cityNo": "1516588857",
        "branchNo": "69174684",
        "gridNo": "66194",
        "cityName": "北区",
        "branchName": "北京",
        "gridName": "北京CBD"
    },
    {
        "cityNo": "1516588858",
        "branchNo": "69174687",
        "gridNo": "66274",
        "cityName": "东区",
        "branchName": "上海",
        "gridName": "上海五角场"
    },
]
var idArray = [];
var newAarray = [];

arrayName.forEach(function (ele, i) {
    if (idArray.indexOf(arrayName[i].branchNo) === -1) {
        newAarray.push({
            'cityNo': arrayName[i].cityNo,
            'branchNo': arrayName[i].branchNo,
            'gridNo': arrayName[i].gridNo,
            'cityName': arrayName[i].cityName,
            'branchName': arrayName[i].branchName,
            'gridName': [arrayName[i].gridName]
        })
        idArray.push(arrayName[i].branchNo);
    } else {
        newAarray.forEach(function (dom, k) {
            if (newAarray[k].branchNo == arrayName[i].branchNo) {
                newAarray[k].gridName.push(arrayName[i].gridName)  //把具有相同branchNo的gridName值进行合并
            }
        })

    }
})
        console.log(arrayName)