parsehex/script.js Secret

## script.js
// tested working in
// chrome (canary) v65
// chrome v63
// firefox v57

var alertSound = document.getElementById('alert-sound');
var audioFixStarted = false;


// uses the same test that PC uses
var scriptHidden = false;
function detectUnfocus() {
	// console.log('checking focus');
	var previousTime = (detectUnfocus.savedTime) || new Date().getTime();
	detectUnfocus.savedTime = new Date().getTime();
	if ((detectUnfocus.savedTime - previousTime) > 900) {
		scriptHidden = true;
		if (!alertSound) console.log('script hidden');
	} else {
		scriptHidden = false;
		if (!alertSound) console.log('script not hidden');
	}
	update();
}
function addExternalScriptCheck() {
	gExtInterval = setInterval(detectUnfocus, 500);
}
addExternalScriptCheck();


// set up and play a quiet low-frequency sound
// browsers won't throttle tabs playing audio
function setupFixSound() {
	// don't need to run this more than once
	if (audioFixStarted) return;
	audioFixStarted = true;

	// this comes from the examples on https://developer.mozilla.org/en-US/docs/Web/API/Web_Audio_API/Using_Web_Audio_API
	var audioCtx = new (window.AudioContext || window.webkitAudioContext)();
	var oscillator = audioCtx.createOscillator();
	var gainNode = audioCtx.createGain();
	oscillator.connect(gainNode);
	gainNode.connect(audioCtx.destination);

	// could try other types besides sine wave
	// triangle sounds okay
	oscillator.type = 'sine';

	// this seems to be about the lowest volume before the browser ignores the sound
	// tested it by lowering and checking if the sound icon showed up on the tab
	// gainNode.gain.setTargetAtTime(0.1, audioCtx.currentTime, 0.1);
	gainNode.gain.setTargetAtTime(0.0004, audioCtx.currentTime, 0);

	// picked a low frequency to make it less noticeable
	// too low and i noticed some audio 'crackling'
	// with 100 there's a slight crackle when the sound starts but that's it
	oscillator.frequency.setTargetAtTime(100, audioCtx.currentTime + 1, 0.5);
	// oscillator.frequency.setTargetAtTime(100, audioCtx.currentTime + 0.1, 0.5);

	oscillator.start();

	// debugging:
	window.stop = function () {
		oscillator.stop();
	};
}

// in later chrome versions, there has to be a user gesture on the page before audio is allowed to play
// clicking in the page works, even pressing a key on the page works
// don't need to listen for the event but you may get errors otherwise
// this also works for playing <audio> tags like in update() below
window.addEventListener('click', setupFixSound);
window.addEventListener('keypress', setupFixSound);
// setupFixSound();

function update() {
	if (alertSound && scriptHidden) alertSound.play();
	else alertSound.pause();
}

## throttle-test.html
<html>

<head>
	<meta charset='utf-8'>
</head>

<body>
	<!-- nothing special, just an mp3 used as an alert if tab is unfocused -->
	<!-- i used one of the beeps from https://www.soundjay.com/beep-sounds-1.html but it doesn't matter -->
	<!-- remove element to just use console.log -->
	<audio id='alert-sound' src='./beep.mp3'></audio>

	<script src='script.js'></script>
</body>

</html>
	// tested working in
	// chrome (canary) v65
	// chrome v63
	// firefox v57

	var alertSound = document.getElementById('alert-sound');
	var audioFixStarted = false;


	// uses the same test that PC uses
	var scriptHidden = false;
	function detectUnfocus() {
	// console.log('checking focus');
	var previousTime = (detectUnfocus.savedTime) \|\| new Date().getTime();
	detectUnfocus.savedTime = new Date().getTime();
	if ((detectUnfocus.savedTime - previousTime) > 900) {
	scriptHidden = true;
	if (!alertSound) console.log('script hidden');
	} else {
	scriptHidden = false;
	if (!alertSound) console.log('script not hidden');
	}
	update();
	}
	function addExternalScriptCheck() {
	gExtInterval = setInterval(detectUnfocus, 500);
	}
	addExternalScriptCheck();


	// set up and play a quiet low-frequency sound
	// browsers won't throttle tabs playing audio
	function setupFixSound() {
	// don't need to run this more than once
	if (audioFixStarted) return;
	audioFixStarted = true;

	// this comes from the examples on https://developer.mozilla.org/en-US/docs/Web/API/Web_Audio_API/Using_Web_Audio_API
	var audioCtx = new (window.AudioContext \|\| window.webkitAudioContext)();
	var oscillator = audioCtx.createOscillator();
	var gainNode = audioCtx.createGain();
	oscillator.connect(gainNode);
	gainNode.connect(audioCtx.destination);

	// could try other types besides sine wave
	// triangle sounds okay
	oscillator.type = 'sine';

	// this seems to be about the lowest volume before the browser ignores the sound
	// tested it by lowering and checking if the sound icon showed up on the tab
	// gainNode.gain.setTargetAtTime(0.1, audioCtx.currentTime, 0.1);
	gainNode.gain.setTargetAtTime(0.0004, audioCtx.currentTime, 0);

	// picked a low frequency to make it less noticeable
	// too low and i noticed some audio 'crackling'
	// with 100 there's a slight crackle when the sound starts but that's it
	oscillator.frequency.setTargetAtTime(100, audioCtx.currentTime + 1, 0.5);
	// oscillator.frequency.setTargetAtTime(100, audioCtx.currentTime + 0.1, 0.5);

	oscillator.start();

	// debugging:
	window.stop = function () {
	oscillator.stop();
	};
	}

	// in later chrome versions, there has to be a user gesture on the page before audio is allowed to play
	// clicking in the page works, even pressing a key on the page works
	// don't need to listen for the event but you may get errors otherwise
	// this also works for playing <audio> tags like in update() below
	window.addEventListener('click', setupFixSound);
	window.addEventListener('keypress', setupFixSound);
	// setupFixSound();

	function update() {
	if (alertSound && scriptHidden) alertSound.play();
	else alertSound.pause();
	}
	<html>

	<head>
	<meta charset='utf-8'>
	</head>

	<body>
	<!-- nothing special, just an mp3 used as an alert if tab is unfocused -->
	<!-- i used one of the beeps from https://www.soundjay.com/beep-sounds-1.html but it doesn't matter -->
	<!-- remove element to just use console.log -->
	<audio id='alert-sound' src='./beep.mp3'></audio>

	<script src='script.js'></script>
	</body>

	</html>