js将数据转为菜单，一个for?

let data = [


    { id: '02', lable: '产品leader', pid: '01' },

    { id: '03', lable: 'UIleader', pid: '01' },
    { id: '07', lable: '产品经理', pid: '02' },

    { id: '04', lable: '技术leader', pid: '01' },
    { id: '21', lable: '技术leader2', pid: '20' },
    { id: '05', lable: '测试leader', pid: '01' },

    { id: '06', lable: '运维leader', pid: '01' },


    { id: '08', lable: '产品经理', pid: '02' },

    { id: '09', lable: 'UI设计师', pid: '03' },

    { id: '10', lable: '前端工程师', pid: '04' },

    { id: '11', lable: '后端工程师', pid: '04' },

    { id: '12', lable: '后端工程师', pid: '04' },

    { id: '13', lable: '测试工程师', pid: '05' },

    { id: '14', lable: '测试工程师', pid: '05' },

    { id: '15', lable: '运维工程师', pid: '06' },

    { id: '01', lable: '项目经理', pid: '' },
    { id: '20', lable: '项目经理22', pid: '' },

]
data.sort(_ => Math.random() - 0.5) //乱序

/**
* 利用浅拷贝
*/
function toData2(arr) {
    let obj = {}, result = [];
    for (let index = 0; index < arr.length; index++) {
        const element = arr[index];
        if (!obj[element.id]) {
            obj[element.id] = element
            obj[element.id].children = []
        }
        if (element.pid && !obj[element.pid]) {
            obj[element.pid] = { children: [] }
        }
        if (!element.pid) {
            element.children = obj[element.id].children
            result.push(element)
        } else {
            obj[element.pid].children.push(element)
        }

    }
    return result
}

function toData3(arr) {
    let obj = {}, result = [];
    arr.forEach(element => {
        if (!obj[element.id]) {
            obj[element.id] = element
            obj[element.id].children = []
        }
        if (element.pid && !obj[element.pid]) {
            obj[element.pid] = { children: [] }
        }
        if (!element.pid) {
            element.children = obj[element.id].children
            result.push(element)
        } else {
            obj[element.pid].children.push(element)
        }
    })
    return result
}





console.time('toData2')
console.log(JSON.stringify(toData2(data)))
console.timeEnd('toData2')

console.time('toData3')
console.log(JSON.stringify(toData3(data)))
console.timeEnd('toData3')