Detect modernizr - Is it being used in the project?

detect-modernizr-use.rb

# Determine the feature list from the custom build URL in the source file, e.g.:
# Build: http://modernizr.com/download/#-fontface-backgroundsize-borderimage-borderradius-boxshadow-flexbox-flexboxlegacy-hsla-multiplebgs-opacity-rgba-textshadow-cssanimations-csscolumns-generatedcontent-cssgradients-cssreflections-csstransforms-csstransforms3d-csstransitions-applicationcache-canvas-canvastext-draganddrop-hashchange-history-audio-video-indexeddb-input-inputtypes-localstorage-postmessage-sessionstorage-websockets-websqldatabase-webworkers-geolocation-inlinesvg-smil-svg-svgclippaths-touch-webgl-cssclasses-teststyles-testprop-testallprops-hasevent-prefixes-domprefixes-load

has_features = [
  "fontface",
  "backgroundsize",
  "borderimage",
  "borderradius",
  "boxshadow",
  "flexbox",
  "flexboxlegacy",
  "hsla",
  "multiplebgs",
  "opacity",
  "rgba",
  "textshadow",
  "cssanimations",
  "csscolumns",
  "generatedcontent",
  "cssgradients",
  "cssreflections",
  "csstransforms",
  "csstransforms3d",
  "csstransitions",
  "applicationcache",
  "canvas",
  "canvastext",
  "draganddrop",
  "hashchange",
  "history",
  "audio",
  "video",
  "indexeddb",
  "input",
  "inputtypes",
  "localstorage",
  "postmessage",
  "sessionstorage",
  "websockets",
  "websqldatabase",
  "webworkers",
  "geolocation",
  "inlinesvg",
  "smil",
  "svg",
  "svgclippaths",
  "touch",
  "webgl",
  "cssclasses",
  "teststyles",
  "testprop",
  "testallprops",
  "hasevent",
  "prefixes",
  "domprefixes",
  "load",
]

no_features = has_features.map do |feature|
  "no-#{feature}"
end

(has_features + no_features).each do |feature|
  as_class = "\\\.#{feature}"
  result = `grep "#{as_class}" -RI app`
  if !result.empty?
    File.write("./tmp/#{feature}", result)
  else
    puts "No matches for: #{feature}"
  end
end