var list =[
        {
            name: '贵州',
            id: '01',
            parent: 0
        },
        {
            name: '白云',
            id: '010101',
            parent: '0101'
        },
        {
            name: '遵义',
            id: '0102',
            parent: '01'
        },

        {
              name: '贵阳',
              id: '0101',
              parent: '01'
          },
      ];

        var result = getTrees(list, 0);

        function getTrees(list, parentId) {
            let items = {};
            // 获取每个节点的直属子节点，*记住是直属，不是所有子节点
            for (let i = 0; i < list.length; i++) {
                let key = list[i].parent;
                if (items[key]) {
                    items[key].push(list[i]);
                } else {
                    items[key] = [];
                    items[key].push(list[i]);
                }
            }
            return formatTree(items, parentId);
        }

        function formatTree(items, parentId) {
            let result = [];
            if (!items[parentId]) {
                return result;
            }
            for (let t of items[parentId]) {
                t.children = formatTree(items, t.id)
                result.push(t);

                if (!t.children.length) {
                    delete t.children;
                }
            }
            
            return result;
        }

        console.log(result);

var list =[
      {
          name: '贵州',
          id: '01',
          parent: 0
      },
      {
          name: '白云',
          id: '010101',
          parent: '0101'
      },
      {
          name: '遵义',
          id: '0102',
          parent: '01'
      },

      {
            name: '贵阳',
            id: '0101',
            parent: '01'
        },
    ];

    function tree(list) {
        var map = {};
        list.forEach((v, i) => {
            map[v.id] = v;
        });

        var result = [];
        list.forEach(function (v, i) {
            var parent = map[v.parent];

            if(parent) {
              (parent.children || (parent.children = [])).push(v);
            } else {
                result.push(v);
            }
        });

        return result;
    }