How to prevent screen sleep using javascript

Question

I have a use case where we donot want the user who is taking a test get sleep timeout while in test which is of 3 hrs. I was looking at nosleep.js but i has cpu overuse problem as it was not working in windows.

I was wondering how test taking apps do it, also how youtube achieves this.

Any help on this is really appreciated

Answer 1

Wake Lock API arrives in Chrome 79. However none of the other browser support this as of now.

https://developers.google.com/web/updates/2019/12/nic79#wake-lock

Answer 2

YouTube handles this by simply playing video. When you play a video with sound in the browser, the browser requests a wake lock automatically so as not to interrupt the user.

It isn't clear from your question what your specific requirements are, but if playing a video is possible, try that.

Answer 3

Play looped VIDEO or AUDIO on your page

You can use this a quick example to add a Fake looped video to your page and prevent mobile device from sleep:

// Create the root video element
var video = document.createElement('video');
video.setAttribute('loop', '');
// Add some styles if needed
video.setAttribute('style', 'position: fixed;');

// A helper to add sources to video
function addSourceToVideo(element, type, dataURI) {
    var source = document.createElement('source');
    source.src = dataURI;
    source.type = 'video/' + type;
    element.appendChild(source);
}

// A helper to concat base64
var base64 = function(mimeType, base64) {
    return 'data:' + mimeType + ';base64,' + base64;
};

// Add Fake sourced
addSourceToVideo(video,'webm', base64('video/webm', 'GkXfo0AgQoaBAUL3gQFC8oEEQvOBCEKCQAR3ZWJtQoeBAkKFgQIYU4BnQI0VSalmQCgq17FAAw9CQE2AQAZ3aGFtbXlXQUAGd2hhbW15RIlACECPQAAAAAAAFlSua0AxrkAu14EBY8WBAZyBACK1nEADdW5khkAFVl9WUDglhohAA1ZQOIOBAeBABrCBCLqBCB9DtnVAIueBAKNAHIEAAIAwAQCdASoIAAgAAUAmJaQAA3AA/vz0AAA='));
addSourceToVideo(video, 'mp4', base64('video/mp4', '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'));

// Append the video to where ever you need
document.body.appendChild(video);

// Start playing video after any user interaction.
// NOTE: Running video.play() handler without a user action may be blocked by browser.
var playFn = function() {
    video.play();
    document.body.removeEventListener('touchend', playFn);
};
document.body.addEventListener('touchend', playFn);

Answer 4

So after dealing with the pain of this problem for nice afternoon. I'm posting my solution. I'm using modules so delete export statements if you're not. My goal was to minimize effect on battery. So I play empty video file (10 x 10px, 1 frame lenght with empty audio track) every 10 seconds. I play it for the first time when user first clicks so the browser will allow me to play it. There are still side effects though. I.e. in Safari, the audio icon will blink and on iPhone lockscreen, the page will be shown as the last one playing video/audio.

let noSleep = null
let video = null


// --- Public ---

export function activate() {
    if (!noSleep) noSleep = new NoSleep()
}

export function deactivate() {
    if (noSleep) {
        noSleep.stop()
        noSleep = null
    }
}


// --- Private ---

class NoSleep {
    constructor() {
        this._noSleep = true
        this._keepAwake()
    }

    stop() {
        this._noSleep = false
    }

    async _keepAwake() {
        while(this._noSleep) {
            if (video) video.play()
            document.body.innerHTML += "<br>Played"
            await wait(10000)
        }
    }
}

window.addEventListener("click", function enable() {
    window.removeEventListener("click", enable)

    // Initialize video element
    video = document.createElement("video")
    video.setAttribute("playsinline", "")

    // Add mp4 source
    let source = document.createElement("source")
    source.src = mp4Src
    source.type = "video/mp4"
    video.append(source)

    // Add webm source
    source = document.createElement("source")
    source.src = webmSrc
    source.type = "video/webm"
    video.append(source)

    // Play it as a result of user interaction
    video.play()
    document.body.innerHTML = "Activated"
    activate()
})

function wait(milliseconds) {
    return new Promise(resolve => setTimeout(resolve, milliseconds))
}

const mp4Src = "data:video/mp4;base64,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"

const webmSrc = "data:video/webm;base64,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"

Implementation is made so multiple calls to activate()/deactivate() have no effect (which was beneficial in my use case). I create NoSleep object to make sure that it's gonna deactivate (operation may take up to 10 seconds to deactivate). Without it quick successive activations and deactivations could result in multiple wake cycles to run at the same time without quiting themselves eventually.