SOURCE

let data=[
    {id:1,name:'部门1',pid:0},
    {id:2,name:'部门6',pid:1},
    {id:3,name:'部门2',pid:1},
    {id:4,name:'部门3',pid:2},
    {id:5,name:'部门4',pid:3},
    {id:6,name:'部门5',pid:4}
]

function parseTree(arr){
    let tmp={}
    for(let item of arr){
        tmp[item.id]=item
    }
    return tmp
}

function test(arr){
    let root
    for(let key in arr){
        if(arr[key].pid===0){
            root=arr[key]
        }else{
            let pNode=arr[arr[key].pid]
            if(!pNode.children){
                pNode.children=[arr[key]]
            }else{
                pNode.children.push(arr[key])
            }
        }
    }
    return root
}

let tmp=parseTree(data)
console.log(tmp)
let tree=test(tmp)
console.log(tree)