线性结构与树形结构相互转换（ES6实现）

线性转树形：

function listConvertTree(list) {
  let root = null;
  if (list && list.length) {
    root = { id: 0, parentId: null, children: [] };
    const group = {};
    for (let index = 0; index < list.length; index += 1) {
      if (list[index].parentId !== null && list[index].parentId !== undefined) {
        if (!group[list[index].parentId]) {
          group[list[index].parentId] = [];
        }
        group[list[index].parentId].push(list[index]);
      }
    }
    const queue = [];
    queue.push(root);
    while (queue.length) {
      const node = queue.shift();
      node.children = group[node.id] && group[node.id].length ? group[node.id] : null;
      if (node.children) {
        queue.push(...node.children);
      }
    }
  }
  return root;
}

树形转线性：

function treeConvertList(root) {
  const list = [];
  if (root) {
    const Root = JSON.parse(JSON.stringify(root));
    const queue = [];
    queue.push(Root);
    while (queue.length) {
      const node = queue.shift();
      if (node.children && node.children.length) {
        queue.push(...node.children);
      }
      delete node.children;
      if (node.parentId !== null && node.parentId !== undefined) {
        list.push(node);
      }
    }
  }
  return list;
}