Detect effective horizontal pixel width on a mobile device with Javascript

So you want to find out how many horizontal pixels you have available on a mobile device. This is super difficult because:

Many Bothan spies had to die for this code:

function effectiveDeviceWidth() {
  var deviceWidth = window.orientation == 0 ? window.screen.width : window.screen.height;
  // iOS returns available pixels, Android returns pixels / pixel ratio
  // http://www.quirksmode.org/blog/archives/2012/07/more_about_devi.html
  if (navigator.userAgent.indexOf('Android') >= 0 && window.devicePixelRatio) {
    deviceWidth = deviceWidth / window.devicePixelRatio;
  }
  return deviceWidth;
}
Henning Koch About 11 years ago