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How to detect if the React app is actually being viewed on mobile menu actions

I have a React app, I've added eventlisteners to the window. So, this way I can detect if the user actually viewing the page or not. On computer browser, everything works as expected.
But I tried this on IphoneX (it's irrelevant but the browser was Safari), and I came across this: If the user holds the bottom of the menu and swipe away all the open ones, then onBlur doesn't work. It stays on the onFocus event. So actually window.eventlistener not working properly on mobile.
Also, when I open the browser again (but not clicking anything, just opening the browser and view the page) onFocus event also not working. It waits for me to touch or click somewhere on the page.
How to handle user focus/blur completely on mobile side?

In the documentation for iOS / Safari supported events, they suggest pageshow and pagehide to listen for the kind of activity that I think you're talking about.

you can use window.navigator to get all OS and browser info

You can use requestAnimationFrame to check if the user is watching the page.
function isWatching(){
console.log("watching: " + Date.now());
requestAnimationFrame(isWatching);
}
requestAnimationFrame(isWatching);
See the example here: https://jsfiddle.net/t2r1sp56/ and you should also read more about it here: https://developer.mozilla.org/en-US/docs/Web/API/window/requestAnimationFrame

You can use visibilityChange event and for the complete compatibility, you need to use webkit, ms, etc. prefix. I hope it helps :)
let visibilityEventName = '';
let hiddenProperty = '';
if (typeof document.hidden !== 'undefined') {
hiddenProperty = 'hidden';
visibilityEventName = 'visibilitychange';
} else if (typeof document.msHidden !== 'undefined') {
hiddenProperty = 'msHidden';
visibilityEventName = 'msvisibilitychange';
} else if (typeof document.webkitHidden !== 'undefined') {
hiddenProperty = 'webkitHidden';
visibilityEventName = 'webkitvisibilitychange';
}
// check whether this API is available or not and then proceed
if (visibilityEventName) {
document.addEventListener(visibilityEventName, () => {
if (document[hiddenProperty]) {
// not visible
} else {
// visible
}
}, false);
}

I have solved the issue using below event listeners.
document.addEventListener("visibilitychange", handleActivity);
document.addEventListener("blur", handleActivityFalse);
window.addEventListener("blur", handleActivityFalse);
window.addEventListener("focus", handleActivityTrue);
document.addEventListener("focus", handleActivityTrue);

Disable mouse movement for Vanilla-tilt.js but keep gyroscope effect

I'm using the plugin Vanilla-tilt.js and on desktop it works great. On mobile the tilt effect responds to the device orientation which is great, but when the user taps somewhere on their device it makes the tilt areas jerk towards where the tap was then return to their original position. I'm using Chrome on Android, feel free to try it yourself with the link above.
I'd like to keep the gyroscope effect on mobile but disable user taps from affecting the tile position. I'm using the inline configuration, here's an example:
<div data-tilt data-tilt-full-page-listening data-tilt-reset="false">Tilt object goes here</div>
My first thought is to download the vanilla-tilt.js source code and modify it so it only looks for mouse events if the screen is a certain width. I don't mind switching to the jQuery version, Tilt.js if that makes this easier.
I built a minified code example that you can view here.

I think you could use something like this document.body.style.pointerEvents = 'none', I am unable to test it though, as I am on PC.

I just noticed that in case of a "tap" the event.movementX and event.movementY are equal to zero, so I believe an easy solution would require to slightly adapt the onMouseMove function, something like this:
onMouseMove(event) {
if(event.movementX == 0 && event.movementY == 0) return false;
if (this.updateCall !== null) {
cancelAnimationFrame(this.updateCall);
}
this.event = event;
this.updateCall = requestAnimationFrame(this.updateBind);
}
In Your example, You are using the built-in autoinitialization. There is more work, this would require to monkey-patch the already attached listeners. Here is how I did it, as a proof of concept:
(function() {
var elements = document.querySelectorAll("[data-tilt]");
elements.forEach(function(item, index){
function onMouseMove(event) {
if(event.movementX == 0 && event.movementY == 0) return false;
if (this.updateCall !== null) {
cancelAnimationFrame(this.updateCall);
}
this.event = event;
this.updateCall = requestAnimationFrame(this.updateBind);
}
var tiltObj = item.vanillaTilt;
tiltObj.elementListener.removeEventListener("mousemove", tiltObj.onMouseMoveBind);
tiltObj.onMouseMoveBind = onMouseMove.bind(tiltObj);
tiltObj.elementListener.addEventListener("mousemove", tiltObj.onMouseMoveBind);
});
})();
Just to be sure, I tested this hotfix with Your minified test-case and with the vanilla-tilt home page and it seems working, but the final solution may vary, depending from Your implementation.
Please, test it in Your mobile device and let me know.

Modernizr.touch returns true on firefox browser

I have written a peace of code to get the event based on touch and non-touch. Its working all other browsers and devices, but Firefox. Default FF return the true.
var thumbsEvent, isTouch = Modernizr.touch; // detect the touch
if(isTouch){
thumbsEvent = 'click';//on touch surface, click
}
else {
thumbsEvent = 'mouseover';//on non touch surface, mouseover
}
Is there a way to manage this issue.
Example fiddle

On behalf of Modernizr - We're really sorry about this.
Modernizr.touch has been renamed Modernizr.touchevents in the yet-to-be-released version 3.0, as it is a far more accurate description of the detect. Basically, all this detect is doing is checking for the existence of touch events, and returning true if they are found. Desktop chrome does the same thing if you enable developer tools. It just means that your version of firefox on your laptop is reporting support of touch events, for several possible reasons.

i had the same issue, this fixed it for me: in firefox go to "about:config", then search for the setting "dom.w3c_touch_events.enabled" and reset that one. i then had to restart firefox and afterwards "Modernizr.touch" correctly returned "false" for me.
source: https://github.com/Modernizr/Modernizr/issues/1225

Have same issue: Modernizr.touch returns true at desktop FireFox 33.1, Mac OS.
My solution: using mobile-first approach, apply all touch-related bells-and-whistles by default. If Modernizr detect .no-touch then apply (or disable) some site features for desktop users.

I had the same issue some time ago.
The problem was that some laptop models come with a version with touchscreen. We found out that if one uses such a model, Modernizr.touch returns true even if this person is using the non-touch laptop model version.
Now, click-events do work on touch devices, but not the other way round. So we worked around this limitation by adding an additional check:
var thumbsEvent, isTouch = Modernizr.touch;
var isAndroid = ...; // Android detection code
var isIOs = ...; // iOS detection code
// touch is only supported on iOS and Android
// devices, which have for sure a touch interface
if(isTouch && (isAndroid || isIOs) ){
thumbsEvent = 'click';
}
else {
thumbsEvent = 'mouseover';
}
That's probably not an optimal solution, because you need to do the device detection with user-agent sniffing instead of feature detection, which was probably why you used Modernizr in the first place.
Also, devices which support touch but are neither iOS nor Android will be excluded from touch events.

There is a temporary fix to this. I was having the same problem so what i did was i did a little digging to find an html5 property which gets detected by FF but not on mobile devices and i found flexbox to be one of them. (Read: http://html5please.com/#flexbox).
So below is the code you can use to have your problem fixed:
var isTouch = Modernizr.touch, // detect the touch
isFlex = Modernizr.flexbox; // detect flexbox
if (isTouch) {
// Detect if FF
if (isFlex) ) {
thumbsEvent = 'mouseover'; //on FF, mouseover
} else {
thumbsEvent = 'click';//on non-FF touch surface, click
}
} else {
thumbsEvent = 'mouseover';//on non touch surface, mouseover
}
Please do note that this is temporary, if mobile devices start supporting flexbox it won't work.

It's a know Firefox Bug at least since FF27: https://bugzilla.mozilla.org/show_bug.cgi?id=970346

How to determine if the client is a touch device [duplicate]

This question already has answers here:
What's the best way to detect a 'touch screen' device using JavaScript?
(37 answers)
Closed 9 years ago.
is there any nice and clean method or trick to find out if the user is on a touch-device or not?
I know there is stuff like
var isiPad = navigator.userAgent.match(/iPad/i) != null;
but I simply wonder if there is a trick to generally determine if the user is on Touch device?
Because there are a lot more touch devices and tablets out there then just iPads.
thank you.

You can use the following JS function:
function isTouchDevice() {
var el = document.createElement('div');
el.setAttribute('ongesturestart', 'return;'); // or try "ontouchstart"
return typeof el.ongesturestart === "function";
}
Source: Detecting touch-based browsing.
Please note the above code only tests if the browser has support for touch, not the device.
Related links:
How to detect a mobile device using jQuery
How to optimize website for touch devices
How to detect a mobile device using jQuery
What's the best way to detect a 'touch screen' device using JavaScript?
Mozilla.org Detecting touch: it’s the ‘why’, not the ‘how’
There may be detection in jquery for mobile and jtouch

Include modernizer, which is a tiny feature detection library. Then you can use something like below.
if (Modernizr.touch){
// bind to touchstart, touchmove, etc and watch `event.streamId`
} else {
// bind to normal click, mousemove, etc
}

if ("ontouchstart" in document.documentElement)
{
alert("It's a touch screen device.");
}
else
{
alert("Others devices");
}
most simple code i found after browsing a lot here and there

Using document.createEvent("TouchEvent") will not work on desktop-devices. So you can use it inside an if statement.
Note that this method could produce errors on non-touch devices. I would prefer checking for ontouchstart in document.documentElement.

Check out this post, it gives a really nice code snippet for what to do when touch devices are detected or what to do if touchstart event is called:
$(function(){
if(window.Touch) {
touch_detect.auto_detected();
} else {
document.ontouchstart = touch_detect.surface;
}
}); // End loaded jQuery
var touch_detect = {
auto_detected: function(event){
/* add everything you want to do onLoad here (eg. activating hover controls) */
alert('this was auto detected');
activateTouchArea();
},
surface: function(event){
/* add everything you want to do ontouchstart here (eg. drag & drop) - you can fire this in both places */
alert('this was detected by touching');
activateTouchArea();
}
}; // touch_detect
function activateTouchArea(){
/* make sure our screen doesn't scroll when we move the "touchable area" */
var element = document.getElementById('element_id');
element.addEventListener("touchstart", touchStart, false);
}
function touchStart(event) {
/* modularize preventing the default behavior so we can use it again */
event.preventDefault();
}

If you use Modernizr, it is very easy to use Modernizr.touch as mentioned earlier.
However, I prefer using a combination of Modernizr.touch and user agent testing, just to be safe.
var deviceAgent = navigator.userAgent.toLowerCase();
var isTouchDevice = Modernizr.touch ||
(deviceAgent.match(/(iphone|ipod|ipad)/) ||
deviceAgent.match(/(android)/) ||
deviceAgent.match(/(iemobile)/) ||
deviceAgent.match(/iphone/i) ||
deviceAgent.match(/ipad/i) ||
deviceAgent.match(/ipod/i) ||
deviceAgent.match(/blackberry/i) ||
deviceAgent.match(/bada/i));
if (isTouchDevice) {
//Do something touchy
} else {
//Can't touch this
}
If you don't use Modernizr, you can simply replace the Modernizr.touch function above with ('ontouchstart' in document.documentElement)
Also note that testing the user agent iemobile will give you broader range of detected Microsoft mobile devices than Windows Phone.
Also see this SO question

What's the best way to detect a 'touch screen' device using JavaScript?

I've written a jQuery plug-in that's for use on both desktop and mobile devices. I wondered if there is a way with JavaScript to detect if the device has touch screen capability. I'm using jquery-mobile.js to detect the touch screen events and it works on iOS, Android etc., but I'd also like to write conditional statements based on whether the user's device has a touch screen.
Is that possible?

UPDATE 2021
To see the old answers: check the history. I decided to start on a clean slate as it was getting out of hands when keeping the history in the post.
My original answer said that it could be a good idea to use the same function as Modernizr was using, but that is not valid anymore as they removed the "touchevents" tests on this PR: https://github.com/Modernizr/Modernizr/pull/2432 due to it being a confusing subject.
With that said this should be a fairly ok way of detecting if the browser has "touch capabilities":
function isTouchDevice() {
return (('ontouchstart' in window) ||
(navigator.maxTouchPoints > 0) ||
(navigator.msMaxTouchPoints > 0));
}
But for more advanced use cases far more smarter persons than me have written about this subject, I would recommend reading those articles:
Stu Cox: You Can't Detect a Touchscreen
Detecting touch: it's the 'why', not the 'how'
Getting touchy presentation by Patrick H. Lauke

Update: Please read blmstr's answer below before pulling a whole feature detection library into your project. Detecting actual touch support is more complex, and Modernizr only covers a basic use case.
Modernizr is a great, lightweight way to do all kinds of feature detection on any site.
It simply adds classes to the html element for each feature.
You can then target those features easily in CSS and JS. For example:
html.touch div {
width: 480px;
}
html.no-touch div {
width: auto;
}
And Javascript (jQuery example):
$('html.touch #popup').hide();

As Modernizr doesn't detect IE10 on Windows Phone 8/WinRT, a simple, cross-browser solution is:
var supportsTouch = 'ontouchstart' in window || navigator.msMaxTouchPoints;
You only ever need to check once as the device won't suddenly support or not support touch, so just store it in a variable so you can use it multiple times more efficiently.

Since the introduction of interaction media features you simply can do:
if(window.matchMedia("(pointer: coarse)").matches) {
// touchscreen
}
https://www.w3.org/TR/mediaqueries-4/#descdef-media-any-pointer
Update (due to comments): The above solution is to detect if a "coarse pointer" - usually a touch screen - is the primary input device. In case you want to dectect if a device with e.g. a mouse also has a touch screen you may use any-pointer: coarse instead.
For more information have a look here: Detecting that the browser has no mouse and is touch-only

Using all the comments above I've assembled the following code that is working for my needs:
var isTouch = (('ontouchstart' in window) || (navigator.msMaxTouchPoints > 0));
I have tested this on iPad, Android (Browser and Chrome), Blackberry Playbook, iPhone 4s, Windows Phone 8, IE 10, IE 8, IE 10 (Windows 8 with Touchscreen), Opera, Chrome and Firefox.
It currently fails on Windows Phone 7 and I haven't been able to find a solution for that browser yet.
Hope someone finds this useful.

I like this one:
function isTouchDevice(){
return window.ontouchstart !== undefined;
}
alert(isTouchDevice());

If you use Modernizr, it is very easy to use Modernizr.touch as mentioned earlier.
However, I prefer using a combination of Modernizr.touch and user agent testing, just to be safe.
var deviceAgent = navigator.userAgent.toLowerCase();
var isTouchDevice = Modernizr.touch ||
(deviceAgent.match(/(iphone|ipod|ipad)/) ||
deviceAgent.match(/(android)/) ||
deviceAgent.match(/(iemobile)/) ||
deviceAgent.match(/iphone/i) ||
deviceAgent.match(/ipad/i) ||
deviceAgent.match(/ipod/i) ||
deviceAgent.match(/blackberry/i) ||
deviceAgent.match(/bada/i));
if (isTouchDevice) {
//Do something touchy
} else {
//Can't touch this
}
If you don't use Modernizr, you can simply replace the Modernizr.touch function above with ('ontouchstart' in document.documentElement)
Also note that testing the user agent iemobile will give you broader range of detected Microsoft mobile devices than Windows Phone.
Also see this SO question

We tried the modernizr implementation, but detecting the touch events is not consistent anymore (IE 10 has touch events on windows desktop, IE 11 works, because the've dropped touch events and added pointer api).
So we decided to optimize the website as a touch site as long as we don't know what input type the user has. This is more reliable than any other solution.
Our researches say, that most desktop users move with their mouse over the screen before they click, so we can detect them and change the behaviour before they are able to click or hover anything.
This is a simplified version of our code:
var isTouch = true;
window.addEventListener('mousemove', function mouseMoveDetector() {
isTouch = false;
window.removeEventListener('mousemove', mouseMoveDetector);
});

There is something better than checking if they have a touchScreen, is to check if they are using it, plus that's easier to check.
if (window.addEventListener) {
var once = false;
window.addEventListener('touchstart', function(){
if (!once) {
once = true;
// Do what you need for touch-screens only
}
});
}

Working Fiddle
I have achieved it like this;
function isTouchDevice(){
return true == ("ontouchstart" in window || window.DocumentTouch && document instanceof DocumentTouch);
}
if(isTouchDevice()===true) {
alert('Touch Device'); //your logic for touch device
}
else {
alert('Not a Touch Device'); //your logic for non touch device
}

This one works well even in Windows Surface tablets !!!
function detectTouchSupport {
msGesture = window.navigator && window.navigator.msPointerEnabled && window.MSGesture,
touchSupport = (( "ontouchstart" in window ) || msGesture || window.DocumentTouch && document instanceof DocumentTouch);
if(touchSupport) {
$("html").addClass("ci_touch");
}
else {
$("html").addClass("ci_no_touch");
}
}

The biggest "gotcha" with trying to detect touch is on hybrid devices that support both touch and the trackpad/mouse. Even if you're able to correctly detect whether the user's device supports touch, what you really need to do is detect what input device the user is currently using. There's a detailed write up of this challenge and a possible solution here.
Basically the approach to figuring out whether a user just touched the screen or used a mouse/ trackpad instead is to register both a touchstart and mouseover event on the page:
document.addEventListener('touchstart', functionref, false) // on user tap, "touchstart" fires first
document.addEventListener('mouseover', functionref, false) // followed by mouse event, ie: "mouseover"
A touch action will trigger both of these events, though the former (touchstart) always first on most devices. So counting on this predictable sequence of events, you can create a mechanism that dynamically adds or removes a can-touch class to the document root to reflect the current input type of the user at this moment on the document:
;(function(){
    var isTouch = false //var to indicate current input type (is touch versus no touch)
    var isTouchTimer
    var curRootClass = '' //var indicating current document root class ("can-touch" or "")
     
    function addtouchclass(e){
        clearTimeout(isTouchTimer)
        isTouch = true
        if (curRootClass != 'can-touch'){ //add "can-touch' class if it's not already present
            curRootClass = 'can-touch'
            document.documentElement.classList.add(curRootClass)
        }
        isTouchTimer = setTimeout(function(){isTouch = false}, 500) //maintain "istouch" state for 500ms so removetouchclass doesn't get fired immediately following a touch event
    }
     
    function removetouchclass(e){
        if (!isTouch && curRootClass == 'can-touch'){ //remove 'can-touch' class if not triggered by a touch event and class is present
            isTouch = false
            curRootClass = ''
            document.documentElement.classList.remove('can-touch')
        }
    }
     
    document.addEventListener('touchstart', addtouchclass, false) //this event only gets called when input type is touch
    document.addEventListener('mouseover', removetouchclass, false) //this event gets called when input type is everything from touch to mouse/ trackpad
})();
More details here.

I used pieces of the code above to detect whether touch, so my fancybox iframes would show up on desktop computers and not on touch. I noticed that Opera Mini for Android 4.0 was still registering as a non-touch device when using blmstr's code alone. (Does anyone know why?)
I ended up using:
<script>
$(document).ready(function() {
var ua = navigator.userAgent;
function is_touch_device() {
try {
document.createEvent("TouchEvent");
return true;
} catch (e) {
return false;
}
}
if ((is_touch_device()) || ua.match(/(iPhone|iPod|iPad)/)
|| ua.match(/BlackBerry/) || ua.match(/Android/)) {
// Touch browser
} else {
// Lightbox code
}
});
</script>

Actually, I researched this question and consider all situations. because it is a big issue on my project too. So I reach the below function, it works for all versions of all browsers on all devices:
const isTouchDevice = () => {
const prefixes = ['', '-webkit-', '-moz-', '-o-', '-ms-', ''];
const mq = query => window.matchMedia(query).matches;
if (
'ontouchstart' in window ||
(window.DocumentTouch && document instanceof DocumentTouch)
) {
return true;
}
return mq(['(', prefixes.join('touch-enabled),('), 'heartz', ')'].join(''));
};
Hint: Definitely, the isTouchDevice just returns boolean values.

Check out this post, it gives a really nice code snippet for what to do when touch devices are detected or what to do if touchstart event is called:
$(function(){
if(window.Touch) {
touch_detect.auto_detected();
} else {
document.ontouchstart = touch_detect.surface;
}
}); // End loaded jQuery
var touch_detect = {
auto_detected: function(event){
/* add everything you want to do onLoad here (eg. activating hover controls) */
alert('this was auto detected');
activateTouchArea();
},
surface: function(event){
/* add everything you want to do ontouchstart here (eg. drag & drop) - you can fire this in both places */
alert('this was detected by touching');
activateTouchArea();
}
}; // touch_detect
function activateTouchArea(){
/* make sure our screen doesn't scroll when we move the "touchable area" */
var element = document.getElementById('element_id');
element.addEventListener("touchstart", touchStart, false);
}
function touchStart(event) {
/* modularize preventing the default behavior so we can use it again */
event.preventDefault();
}

I would avoid using screen width to determine if a device is a touch device. There are touch screens much larger than 699px, think of Windows 8. Navigatior.userAgent may be nice to override false postives.
I would recommend checking out this issue on Modernizr.
Are you wanting to test if the device supports touch events or is a touch device. Unfortunately, that's not the same thing.

No, it's not possible. The excellent answers given are only ever partial, because any given method will produce false positives and false negatives. Even the browser doesn't always know if a touchscreen is present, due to OS APIs, and the fact can change during a browser session, particularly with KVM-type arrangements.
See further details in this excellent article:
http://www.stucox.com/blog/you-cant-detect-a-touchscreen/
The article suggests you reconsider the assumptions that make you want to detect touchscreens, they're probably wrong. (I checked my own for my app, and my assumptions were indeed wrong!)
The article concludes:
For layouts, assume everyone has a touchscreen. Mouse users can use
large UI controls much more easily than touch users can use small
ones. The same goes for hover states.
For events and interactions, assume anyone may have a touchscreen.
Implement keyboard, mouse and touch interactions alongside each other,
ensuring none block each other.

Many of these work but either require jQuery, or javascript linters complain about the syntax. Considering your initial question asks for a "JavaScript" (not jQuery, not Modernizr) way of solving this, here's a simple function that works every time. It's also about as minimal as you can get.
function isTouchDevice() {
return !!window.ontouchstart;
}
console.log(isTouchDevice());
One last benefit I'll mention is that this code is framework and device agnostic. Enjoy!

I think the best method is:
var isTouchDevice =
(('ontouchstart' in window) ||
(navigator.maxTouchPoints > 0) ||
(navigator.msMaxTouchPoints > 0));
if(!isTouchDevice){
/* Code for touch device /*
}else{
/* Code for non touch device */
}

It looks like Chrome 24 now support touch events, probably for Windows 8. So the code posted here no longer works. Instead of trying to detect if touch is supported by the browser, I'm now binding both touch and click events and making sure only one is called:
myCustomBind = function(controlName, callback) {
$(controlName).bind('touchend click', function(e) {
e.stopPropagation();
e.preventDefault();
callback.call();
});
};
And then calling it:
myCustomBind('#mnuRealtime', function () { ... });
Hope this helps !

All browser supported except Firefox for desktop always TRUE because of Firefox for desktop support responsive design for developer even you click Touch-Button or not!
I hope Mozilla will fix this in next version.
I'm using Firefox 28 desktop.
function isTouch()
{
return !!("ontouchstart" in window) || !!(navigator.msMaxTouchPoints);
}

jQuery v1.11.3
There is a lot of good information in the answers provided. But, recently I spent a lot of time trying to actually tie everything together into a working solution for the accomplishing two things:
Detect that the device in use is a touch screen type device.
Detect that the device was tapped.
Besides this post and Detecting touch screen devices with Javascript, I found this post by Patrick Lauke extremely helpful: https://hacks.mozilla.org/2013/04/detecting-touch-its-the-why-not-the-how/
Here is the code...
$(document).ready(function() {
//The page is "ready" and the document can be manipulated.
if (('ontouchstart' in window) || (navigator.maxTouchPoints > 0) || (navigator.msMaxTouchPoints > 0))
{
//If the device is a touch capable device, then...
$(document).on("touchstart", "a", function() {
//Do something on tap.
});
}
else
{
null;
}
});
Important! The *.on( events [, selector ] [, data ], handler ) method needs to have a selector, usually an element, that can handle the "touchstart" event, or any other like event associated with touches. In this case, it is the hyperlink element "a".
Now, you don't need to handle the regular mouse clicking in JavaScript, because you can use CSS to handle these events using selectors for the hyperlink "a" element like so:
/* unvisited link */
a:link
{
}
/* visited link */
a:visited
{
}
/* mouse over link */
a:hover
{
}
/* selected link */
a:active
{
}
Note: There are other selectors as well...

The problem
Due to hybrid devices which use a combination of touch and mouse input, you need to be able dynamically change the state / variable which controls whether a piece of code should run if the user is a touch user or not.
Touch devices also fire mousemove on tap.
Solution
Assume touch is false on load.
Wait until a touchstart event is fired, then set it to true.
If touchstart was fired, add a mousemove handler.
If the time between two mousemove events firing was less than 20ms, assume they are using a mouse as input. Remove the event as it's no longer needed and mousemove is an expensive event for mouse devices.
As soon as touchstart is fired again (user went back to using touch), the variable is set back to true. And repeat the process so it's determined in a dynamic fashion. If by some miracle mousemove gets fired twice on touch absurdly quickly (in my testing it's virtually impossible to do it within 20ms), the next touchstart will set it back to true.
Tested on Safari iOS and Chrome for Android.
Note: not 100% sure on the pointer-events for MS Surface, etc.
Codepen demo
const supportsTouch = 'ontouchstart' in window;
let isUsingTouch = false;
// `touchstart`, `pointerdown`
const touchHandler = () => {
isUsingTouch = true;
document.addEventListener('mousemove', mousemoveHandler);
};
// use a simple closure to store previous time as internal state
const mousemoveHandler = (() => {
let time;
return () => {
const now = performance.now();
if (now - time < 20) {
isUsingTouch = false;
document.removeEventListener('mousemove', mousemoveHandler);
}
time = now;
}
})();
// add listeners
if (supportsTouch) {
document.addEventListener('touchstart', touchHandler);
} else if (navigator.maxTouchPoints || navigator.msMaxTouchPoints) {
document.addEventListener('pointerdown', touchHandler);
}

Right so there is a huge debate over detecting touch/non-touch devices. The number of window tablets and the size of tablets is increasing creating another set of headaches for us web developers.
I have used and tested blmstr's answer for a menu. The menu works like this: when the page loads the script detects if this is a touch or non touch device. Based on that the menu would work on hover (non-touch) or on click/tap (touch).
In most of the cases blmstr's scripts seemed to work just fine (specifically the 2018 one). BUT there was still that one device that would be detected as touch when it is not or vice versa.
For this reason I did a bit of digging and thanks to this article I replaced a few lines from blmstr's 4th script into this:
function is_touch_device4() {
if ("ontouchstart" in window)
return true;
if (window.DocumentTouch && document instanceof DocumentTouch)
return true;
return window.matchMedia( "(pointer: coarse)" ).matches;
}
alert('Is touch device: '+is_touch_device4());
console.log('Is touch device: '+is_touch_device4());
Because of the lockdown have a limited supply of touch devices to test this one but so far the above works great.
I would appreceate if anyone with a desktop touch device (ex. surface tablet) can confirm if script works all right.
Now in terms of support the pointer: coarse media query seems to be supported. I kept the lines above since I had (for some reason) issues on mobile firefox but the lines above the media query do the trick.
Thanks

var isTouchScreen = 'createTouch' in document;
or
var isTouchScreen = 'createTouch' in document || screen.width <= 699 ||
ua.match(/(iPhone|iPod|iPad)/) || ua.match(/BlackBerry/) ||
ua.match(/Android/);
would be a more thorough check I suppose.

I use:
if(jQuery.support.touch){
alert('Touch enabled');
}
in jQuery mobile 1.0.1

You can install modernizer and use a simple touch event. This is very effective and works on every device I have tested it on including windows surface!
I've created a jsFiddle
function isTouchDevice(){
if(Modernizr.hasEvent('touchstart') || navigator.userAgent.search(/Touch/i) != -1){
alert("is touch");
return true;
}else{
alert("is not touch");
return false;
}
}

I also struggled a lot with different options on how to detect in Javascript whether the page is displayed on a touch screen device or not.
IMO, as of now, no real option exists to detect the option properly.
Browsers either report touch events on desktop machines (because the OS maybe touch-ready), or some solutions don't work on all mobile devices.
In the end, I realized that I was following the wrong approach from the start:
If my page was to look similar on touch and non-touch devices, I maybe shouldn't have to worry about detecting the property at all:
My scenario was to deactivate tooltips over buttons on touch devices as they lead to double-taps where I wanted a single tap to activate the button.
My solution was to refactor the view so that no tooltip was needed over a button, and in the end I didn't need to detect the touch device from Javascript with methods that all have their drawbacks.

The practical answer seems to be one that considers the context:
1) Public site (no login)
Code the UI to work with both options together.
2) Login site
Capture whether a mouse-move occurred on the login form, and save this into a hidden input. The value is passed with the login credentials and added to the user's session, so it can be used for the duration of the session.
Jquery to add to login page only:
$('#istouch').val(1); // <-- value will be submitted with login form
if (window.addEventListener) {
window.addEventListener('mousemove', function mouseMoveListener(){
// Update hidden input value to false, and stop listening
$('#istouch').val(0);
window.removeEventListener('mousemove', mouseMoveListener);
});
}
(+1 to #Dave Burt and +1 to #Martin Lantzsch on their answers)

Extent jQuery support object:
jQuery.support.touch = 'ontouchend' in document;
And now you can check it anywhere, like this:
if( jQuery.support.touch )
// do touch stuff