We can do some fun stuff in Node.JS with asynchronous programming. With closures, we can pull a document collection from a NoSQL database, manipulate the results, and push it to an array stored via closure in the parent scope.

closureNoSQL.coffee

require './nosql'  
require 'async'

# new results array.  this will be available via closure
results = []

# Start the NoSQL connection
nosql.connect ()->
  
  # Get the collection pointer
  collection = nosql.getCollection 'collection'
  
  # Find the documents
  collection.find {}, (documents)->
    
    # Create our iterator fn to be consumed by the async library
    eachDocument = (doc, cb)->
      
      # Do something to doc; add/remove/modify variables.
      # Push it to the results array that is in a 
      # parent scope and available via closure.
      results.push doc
      
    async.forEach documents, eachDocument, ()->
      
      # At this point, we have finished getting and dealing with documents.
      # We can close the db and deal with the results.
      nosql.close()
      
      # If we were writing this in an express route, use res.send
      res.send { success: true, results: results }