扁平菜单数据转树形菜单

function arrayToTree(items) {
  const result = [];  
  const itemMap = {};  
    
  // 先转成map存储
  for (const item of items) {
    itemMap[item.id] = {...item, children: []}
  }
  
  for (const item of items) {
    const id = item.id;
    const pid = item.pid;
    const treeItem =  itemMap[id];
    if (pid === 0) {
      result.push(treeItem);
    } else {
      if (!itemMap[pid]) {
        itemMap[pid] = {
          children: [],
        }
      }
      itemMap[pid].children.push(treeItem)
    }

  }
  return result;
}