SOURCE

let arr = [
    { id: 8, name: '部门1', pid: 10 },
    { id: 1, name: '部门1', pid: 0 },
    { id: 2, name: '部门2', pid: 1 },
    { id: 3, name: '部门3', pid: 1 },
    { id: 4, name: '部门4', pid: 3 },
    { id: 5, name: '部门5', pid: 4 },
    { id: 6, name: '部门5', pid: 4 },
]

function arrToTree(arr) {
    const map = {}
    const arrWithMap = arr.map(item => {
        let res = { ...item }
        res.children = []
        map[res.id] = res
        return res
    })
    const tree = []
    arrWithMap.forEach(item => {
        const parent = map[item.pid]
        if (!parent) {
            tree.push(item)
            return
        }
        parent.children.push(item)
    })
    return tree
}


let tree = arrToTree(arr)

console.log(tree)