Mongo reorder list

changeOrder.js

/**
 * model - `Item`
 * order property — `order`
 */

const changeOrder = async (req, res) => {
  try {
    const { itemId } = req.params
    const orderOnClient = Number(req.body.order)

    const items = await Item.find({})
      .sort({ order: 1 })
      .lean()
      .exec()

    // Find place where reordered Item will be replaced
    const newOrder = items[orderOnClient - 1].order

    const updatingItem = await Item.update({ _id: itemId }, { order: newOrder })
      .lean()
      .exec()

    // Reorder other items according order changes
    let query
    let data

    if (updatingItem.order > newOrder) {
      // updatingItem was moved up
      query = {
        _id: { $nin: itemId },
        order: {
          $gte: newOrder,
          $lt: updatingItem.order,
        },
      }
      data = { $inc: { order: 1 } }
    } else {
      // updatingItem was moved down
      query = {
        _id: { $nin: itemId },
        order: {
          $gt: updatingItem.order,
          $lte: newOrder,
        },
      }
      data = { $inc: { order: -1 } }
    }

    await Item.updateMany(query, data)
      .lean()
      .exec()

    const updatedItems = await Item.find({})
      .sort({ order: 1 })
      .lean()
      .exec()

    res.json(updatedItems)
  } catch (e) {
    res.status(500)
  }
}