//嵌套目录层级
//将具有父id的对象数组转换为对象嵌套结构
//参考：https://stackoverflow.com/questions/18017869/build-tree-array-from-flat-array-in-javascript
//list为待转换的对象数组，key为表示父id的键名
function doListToTree(list,key='father_id') {
    let map = {}, outData = [];
    list.map((item,index)=>{
        map[list[index].id] = index; // 初始化map
        list[index].children = []; // 初始化children
    })
    list.map((item)=>{
        if (item[key] !== 0) {
            // 检查 map[item[key]] 是否存在，以判断悬垂的分支（父id不存在的分支）
            // 出现此问题一般是由于父id已删除，但是没有删除掉其子id
            if(map[item[key]]===undefined){
                console.log('悬垂的分支 -> ',item);
                //TODO: 向错误监控平台报告错误
            }else{
                list[map[item[key]]].children.push(item);
            }
        } else {
            outData.push(item);
        }
    })
    return outData;
}

输入：

let menu = [
    {"id":12,"parentId":0},
    {"id":6,"parentId":12},
    {"id":7,"parentId":12},
    {"id":8,"parentId":7},
    {"id":18,"parentId":8},
    {"id":28,"parentId":18},
    {"id":9,"parentId":0},
    {"id":11,"parentId":9},
    {"id":15,"parentId":88}
];
console.log(doListToTree(menu,'parentId'));

输出：

[{
    "id": 12,
    "parentId": 0,
    "children": [{
        "id": 6,
        "parentId": 12,
        "children": []
    }, {
        "id": 7,
        "parentId": 12,
        "children": [{
            "id": 8,
            "parentId": 7,
            "children": [{
                "id": 18,
                "parentId": 8,
                "children": [{
                    "id": 28,
                    "parentId": 18,
                    "children": []
                }]
            }]
        }]
    }]
}, {
    "id": 9,
    "parentId": 0,
    "children": [{
        "id": 11,
        "parentId": 9,
        "children": []
    }]
}]