将一维数组转为树结构的数据

let allRes = [
    {id: 1, title: "公司",expand:true, pid: 0},
    {id: 60, title: "总经理",expand:true, pid: 1},
    {id: 66, title: "业务1部",expand:true, pid: 1},
    {id: 76, title: "总经理助理1", expand:true,pid: 60},
    {id: 77, title: "总经理助理2", expand:true,pid: 66},
    {id: 63, title: "财务部",expand:true, pid: 1},
    {id: 64, title: "会计", expand:true, pid: 63},
    {id: 65, title: "出纳",expand:true,  pid: 63},
    {id: 68, title: "总监",expand:true, pid: 66},
    {id: 70, title: "总监", expand:true,pid: 67},
    {id: 81, title: "test",expand:true, pid: 67},
    {id: 71, title: "业务员",expand:true, pid: 66},
    {id: 75, title: "会计员", expand:true, pid: 64}
];

let result = allRes.reduce(function(prev, item) {

    prev[item.pid] ? prev[item.pid].push(item) : prev[item.pid] = [item];
    return prev;
}, {});
for (let prop in result) {
    console.log(result[prop])
    result[prop].forEach(function(item, i) {
        result[item.id] ? item.children = result[item.id] : ''
    });
}

result = result[0];