isLandscape function to determine whether device is landscape orientation

orientation.js

function isLandscape() {
  var object = window.screen.orientation || window.screen.msOrientation || window.screen.mozOrientation || null;
  if (object) {
    if (object.type.indexOf('landscape') !== -1) { return true; }
    if (object.type.indexOf('portrait') !== -1) { return false; }
  }
  if ('orientation' in window) {
    var value = window.orientation;
    if (value === 0 || value === 180) {
      return false;
    } else if (value === 90 || value === 270) {
      return true;
    }
  }
  // fallback to comparing width to height
  return window.innerWidth > window.innerHeight;
}