Optimizing nested collection calls in mongoDb

Im gettin all my registered items and then Im showing a little user rating section under each item listed on the page. Problem is that collection calls are asyn and I cannot send express response when calls are completed. I used quite a bad way to accomplish that by using timeout, so Im looking for better solution suggestions.

router.route('/').get((request, response) => {
      let collection = []
      Item.find({}, function (err, data) {
        if (!err) {
          data.forEach((item) => {
            User.findOne({_id: item.seller}, function (err, res) {
              if (!err) {
                let parse = JSON.parse(JSON.stringify(item))
                let filter
                switch (item.category) {
                  case 'Relics & Antiques':
                    filter = 'antique'
                    break
                  case 'Coin & Currency':
                    filter = 'currency'
                    break
                  case 'Real Estate':
                    filter = 'realestate'
                    break
                  case 'Sports Memorabilia':
                    filter = 'sports'
                    break
                  case 'Fine Art':
                    filter = 'art'
                    break
                  case 'Jewellery':
                    filter = 'jewel'
                    break
                  case 'Automobile':
                    filter = 'auto'
                    break
                }
                parse.rep = res.rep
                parse.sellerName = res.username
                parse.sellerAvatar = res.avatarURI
                parse.filter = filter
                collection.push(parse)
              }
            })
          })
          setTimeout(() => {
            response.render('home/index', {item: collection})
          }, 500)
        }
      })
    })

I've solved the problem thanks to following SO post: how can run mongoose query in forEach loop

var mongoose = require('mongoose')
mongoose.Promise = require('bluebird')

router.route('/').get((request, response) => {
  let itemCollection = []
  Item.find({}).then((data) => {
    let userCollection = []
    data.forEach((item) => {
      userCollection.push(User.findOne({_id: item.seller}))
      itemCollection.push(item)
    })
    return Promise.all(userCollection, itemCollection)
  }).then((users) => {
    let results = []
    itemCollection.forEach(function (item, index) {
      let parse = JSON.parse(JSON.stringify(item))
      let filter
      switch (item.category) {
        case 'Relics & Antiques':
          filter = 'antique'
          break
        case 'Coin & Currency':
          filter = 'currency'
          break
        case 'Real Estate':
          filter = 'realestate'
          break
        case 'Sports Memorabilia':
          filter = 'sports'
          break
        case 'Fine Art':
          filter = 'art'
          break
        case 'Jewellery':
          filter = 'jewel'
          break
        case 'Automobile':
          filter = 'auto'
          break
      }
      parse.rep = users[index].rep
      parse.sellerName = users[index].username
      parse.sellerAvatar = users[index].avatarURI
      parse.filter = filter
      results.push(parse)
    })
    response.render('home/index', {item: results})
  })
})