Helper to detect and write dependency versions in query string params.

dynamic-dependencies.coffee

# Get version strings from URL
jQueryVersion = /jquery=([\w\.]+)/.exec location.search
backboneVersion = /backbone=([\w\.]+)/.exec location.search
underscoreVersion = /underscore=([\w\.]+)/.exec location.search
mustacheVersion = /mustache=([\w\.]+)/.exec location.search


supportedVersions =
  jquery: ['1.6.4', '1.8.1']
  backbone: ['0.5.3', '0.9.2']
  underscore: ['1.3.3']
  mustache: ['0.5.0-dev']


setVersion = (dep, version) ->
  possibleVersions = supportedVersions[dep]
  versionIsSupported = version and possibleVersions.indexOf(version[1]) isnt -1
  return version[1] if versionIsSupported
  latestVersion = possibleVersions[possibleVersions.length - 1]


# Define `Array.prototype.indexOf` for browsers without it natively (IE)
if !Array::indexOf
  Array::indexOf = (obj, start) ->
    i = start or 0
    j = @length

    while i < j
      return i if @[i] is obj
      i++
    -1


document.write "<script src=\"/vendor/jquery/jquery-#{setVersion 'jquery', jQueryVersion}.js\"><\/script>"
document.write "<script src=\"/vendor/underscore/underscore-#{setVersion 'underscore', underscoreVersion}.js\"><\/script>"
document.write "<script src=\"/vendor/mustache/mustache-#{setVersion 'mustache', mustacheVersion}.js\"><\/script>"
document.write "<script src=\"/vendor/backbone/backbone-#{setVersion 'backbone', backboneVersion}.js\"><\/script>"