SOURCE

const list = [
    { id: 1, name: '西药', parentId: 0 },
    { id: 2, name: '中药', parentId: 0 },
    { id: 3, name: '中成药', parentId: 0 },
    { id: 4, name: '阿莫西林胶囊', parentId: 1 },
    { id: 5, name: '奥美拉唑', parentId: 1 },
    { id: 6, name: '人参', parentId: 2 },
    { id: 7, name: '当归', parentId: 2 },
    { id: 8, name: '祛湿颗粒', parentId: 6 },
    { id: 8, name: '复方甘草片', parentId: 6 }
]

function convert1() {
    const tree = []
    for (let i = 0, len = list.length; i < len; i++) {
        if (list[i].parentId === 0) {
            tree.push(list[i])
        } else {
            for (let j = 0, jlen = tree.length; j < jlen; j++) {
                if (list[i].parentId === tree[j].id) {
                    if (!tree[j].children) {
                        tree[j].children = [list[i]]
                    } else {
                        tree[j].children.push(list[i])
                    }
                }
            }
        }
    }
}

const a = {}

function convert2() {
    const tree2 = []
    const map = {}
    list.forEach(item => {
        map[item.id] = item
    })
    debugger
    list.forEach(item => {
        if (item.parentId !== 0) {
            // map[item.parentId]就会指向map[item.id]
            // parentId绑定的就是父级的id
            map[item.parentId]['children']
                ? map[item.parentId]['children'].push(item)
                : map[item.parentId]['children'] = [item]
        } else {
            tree2.push(item)
        }
    })
    // console.log(map)
    console.log(tree2)
}

function convert3(list, topId = 0) {
    const result = [];
    const map = {};

    list.forEach(item => {
        const { id, parentId } = item;

        if (parentId === topId) {
            result.push(item);
        } else {
            map[parentId] = map[parentId] || [];
            map[parentId].push(item)
        }

        item.children = item.children || map[id] || (map[id] = [])

    })

    return result;

}

// console.log(convert2(list))

const commentlist = [
    {
        parentId: 0,
        id: 1,
        comment: '评论1'
    }, 
    {
        parentId: 1,
        id: 2,
        comment: '评论1的回复评论'
    },
    {
        parentId: 0,
        id: 3,
        comment: '评论2'
    },
    {
        parentId: 2,
        id: 4,
        comment: '评论1的回复的回复'
    },
    {
        parentId: 0,
        id: 5,
        comment: '评论3'
    },
     {
        parentId: 5,
        id: 6,
        comment: '评论3的回复'
    }
]

function flat3(arr) {
    let arrs = []; 
    arr.forEach(item => {
        // console.log(item)
        if (Array.isArray(item.children)) {
            console.log('cc')
            arrs.push(...flat3(item.children))
        } else {
            arrs.push(item)
        }
    })
    return arrs
}



function cc(list) {
    const map = {}
    const arr = []
    // console.log(list)
    list.forEach(item => {
        if (item.parentId === 0) {
            arr.push(item)
        } else {
            map[item.parentId] = map[item.parentId] || [];
            map[item.parentId].push(item)
        }

         item.children = item.children || map[item.id] || (map[item.id] = [])
    })

    arr.forEach(item => {
        console.log(item)
        item.children = flat3(arr.children)
        return item
    })
    // console.log(arr)
    // console.log('map', map)
    // console.log('arr', arr)

   
}
cc(commentlist)