Prevent Android chrome from going idle / auto-locking / sleeping phone?

We strongly don't encourage developers to do this at all. However it is possible. You can simply have a video playing on the page and the device won't go to sleep. This means you could have single frame video set to auto-loop and play (requires a user interaction)

Richard Tibbett has created NoSleep.js to simplify the process for developers.

JavaScript in Chrome on Android (7.0) indeed shuts down after 5 min in sleep mode. Aaargh!

To prevent that, we need e.g. an audio object:

<audio id="dummyAudio">
   <source src="silent.ogg" type="audio/ogg">
   <source src="silent.mp3" type="audio/mpeg">
</audio>

and play it at regular intervals:

function playDummyAudio() { dummyAudio.play(); }    
$(function() {
   var dummyAudio = document.querySelector('#dummyAudio');
   window.setInterval(playDummyAudio, 60 * 1000);
}

Note that the Audio object has to be "unlocked" in a user gesture callback. This can be accomplished e.g. by having a grey CSS overlay with a big fat dummy "Start" button, whose onClick() callback only hides the overlay and calls dummyAudio.load().