eme-2.js

// Try PlayReady
navigator.requestMediaKeySystemAccess('com.microsoft.playready', [{
	initDataTypes: ['keyids', 'cenc'],
	audioCapabilities: [{ contentType: 'audio/mp4; codecs="mp4a"' }],
	videoCapabilities: [{ contentType: 'video/mp4; codecs="avc1"' }]
}
]).then(function (keySystemAccess) { /* Promise succeeded. Call createMediaKeys */},function () {
	// Promise was rejected for PlayReady. Try Widevine.
	navigator.requestMediaKeySystemAccess('com.widevine.alpha', [{
	initDataTypes: ['keyids', 'webm'],
	audioCapabilities: [{ contentType: 'audio/webm; codecs="opus"'}],
	videoCapabilities: [{ contentType: 'video/webm; codecs="vp9"'}]
}
]).then(function (keySystemAccess) { /* Promise succeeded. Call createMediaKeys */ }, function () {
	// Neither Promise succeeded. Browser does not support Widevine or PlayReady
	});
});