Pass additional parameters into jQueryUI autocomplete widget in rails 3.1 coffeescript

autocomplete.js.coffee

#turn on our autocompletes if there are any
jQuery ->
	if $('#user_autocomplete').length
		index = 1
		$('#user_autocomplete').autocomplete
			source: (request, response) ->
				#add our custom index parameter to the call
				request["index"] = index++
				#make our request and handle the response as normal
				$.ajax( 
					url: "/users/autocomplete",
					dataType: "json",
					data: request
					,
					success: (data)->
						response(data)
				)
			select: (event,ui) ->
				#when the close callback is called, we know it was due to selection not focus
				@selected = true
				#append our custom html to the dom
				$(ui.item.html)
					.appendTo('#user_alerts')
					.hide()
					.fadeIn()
			close: () ->
				if @selected
					#clear whatever the user entered, if this closed due to a selection
					$('#user_autocomplete').val("")
					@selected = false

The goal here was to have a text field with the autocomplete widget which would pass additional parameters to the server. The server code renders custom html into the response which can then be added to the page.