user id to name

Template.chatLine.helpers
  username: ->
    username = userIdsToUserNames[@userId]
    return username if username        
    console.log "searching for id #{@userId}"
    user = Meteor.users.findOne(_id: @userId)
    if user?
      userIdsToUserNames[@userId] = user.username
      return user.username
    else
      return 'unknown'