实现列表转树的convert方法

时间复杂度为O(n):

其他遍历

function convert(list) {
	const res = []
	const map = list.reduce((res, v) => (res[v.id] = v, res), {})
	for (const item of list) {
		if (item.parentId === 0) {
			res.push(item)
			continue
		}
		if (item.parentId in map) {
			const parent = map[item.parentId]
			parent.children = parent.children || []
			parent.children.push(item)
		}
	}
	return res
}

深度遍历：

function convert(source, parentId = 0){
    let trees = [];
    for (let item of source) {
      if(item.parentId === parentId) {
        let children = convert(source, item['id']);
        if(children.length) {
          item.children = children
        }
        trees.push(item);
      }
    }
    return trees;
  }

let list =[
    {id:1,name:'部门A',parentId:0},
    {id:2,name:'部门B',parentId:0},
    {id:3,name:'部门C',parentId:1},
    {id:4,name:'部门D',parentId:1},
    {id:5,name:'部门E',parentId:2},
    {id:6,name:'部门F',parentId:3},
    {id:7,name:'部门G',parentId:2},
    {id:8,name:'部门H',parentId:4}
];

const result = convert(list);