Trigger twitter typeahead when another field is completed

Question

I have two fields. One is bound with typeahead. But I want to trigger request, only when another field is not empty (to pass that value as well).

How can I do that? I use Bloodhound as well.

Thanks in advance.

My code (CoffeeScript):

$("[data-word-search-url]").each(->
    search = $(this)
    lang = $("##{search.data("typeahead-lang")}")
    name = search.data("typeahead-name")
    url = search.data("word-search-url")
    source = new Bloodhound(
      name: name
      datumTokenizer: Bloodhound.tokenizers.whitespace
      queryTokenizer: Bloodhound.tokenizers.whitespace
      remote: {
        url: url
        rateLimitWait: 500
        replace: (url, uriEncodedQuery) ->
          url += "?query=#{uriEncodedQuery}&lang=#{lang.val() or ''}"
          return url
      }
    )
    search.typeahead({
      minLength: 2,
      hint: false
    },
      name: name
      displayKey: 'name',
      limit: 0
      source: source
    )
)