Tips & Tricks – Jon Wallsten

We have all been there! You make a responsive web site, add some hover effects as usual.
You try out the site on your touch device, and suddenly strange things start to happens to all kinds of elements when you scroll.
That’s because as soon as you touch the elements, but don’t click them, the browser triggers the hover state.

A lot of really good developers out there want us to treat the desktop users and the touch users the same. But they don’t have the same possibilities, so why?. Just because touch users can’t use the hover state properly, doesn’t mean we shouldn’t aid the desktop users. It helps a lot when navigation around a page!

However, when you use hover effects, beware that your touch users won’t get any help from it. So don’t, for example, rely on tool tips and let the touch users hang dry.

So to allow the desktop users and touch devices to coexist we simply remove the hover effects for touch devices.
It would be super simple if you could use Modernizr to test whether it’s a touch device or not.

But you can’t This method cannot be trusted. There are just to many false positives stacking up.

For example, with the update of Firefox to version 36, my desktop at work report that it’s a touch device. So is Chrome on one of the laptops the testers use in my project.

The only way you can reliably detect a touch device, that I know of, is to listen for an actual touch.
To do this can use a the JavaScript below.

First do I quick and dirty check in case you need to condition something during page load, and the we add a touch test which will only be fire in case a user actually has a touch device.

Note: The second test will not fire until the user actually touch the screen.

(function() {
    //I use jQuery for simplicity
    var preliminaryTouch = false;

    //Assume all devices are no touch device
    $('html').addClass('no-touch-device');

    //Check the user agent string
    if( /Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(navigator.userAgent) ) {
        preliminaryTouch = true;
    }

    if( preliminaryTouch ) {
        //Do something for touch devices and 
        //Add a preliminary touch class
        $('html').addClass('prel-touch-device');
    }
})();

$(document).on('touchstart', function() {
    //Now we can safely remove the the no-touch-device and prel-touch-device classes
    $('html').removeClass('no-touch-device prel-touch-device').addClass('touch-device');
});

//Do something later somewhere in your code
if( $('html').hasClass('touch-device') ) {
    //Do something for touch devices
}

(function() {

//I use jQuery for simplicity

var preliminaryTouch = false;

//Assume all devices are no touch device

$('html').addClass('no-touch-device');

//Check the user agent string

if( /Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(navigator.userAgent) ) {

preliminaryTouch = true;

}

if( preliminaryTouch ) {

//Do something for touch devices and

//Add a preliminary touch class

$('html').addClass('prel-touch-device');

}

})();

$(document).on('touchstart', function() {

//Now we can safely remove the the no-touch-device and prel-touch-device classes

$('html').removeClass('no-touch-device prel-touch-device').addClass('touch-device');

});

//Do something later somewhere in your code

if( $('html').hasClass('touch-device') ) {

//Do something for touch devices

}

Please also note that until we actually know if it’s a real test device or not, the divice will be both touch device and not. Like Schrödinger’s cat or a quantum state.

So now we have the JavaScript in place. Lets move on to the CSS.

You can use the following states, although you should try to avoid using anything else then the ‘no-touch-device’ class, which is the default class for all devices before the test is done.

html.no-touch-device {
    /* This style will be applied form the beginning, and continue to exist unless the second test shows it's a touch device */
}

html.prel-touch-device {
    /* If the preliminary test shows it's a touch device you can use this to apply styles. This will rarely be used in the CSS. But might be handy in the JavaScript early on in the code flow. */
}

html.touch-device {
    /* Here you add the styles that only the touch devices should use. Try to avoid it as much as possible. */
}

html.no-touch-device {

/* This style will be applied form the beginning, and continue to exist unless the second test shows it's a touch device */

}

html.prel-touch-device {

/* If the preliminary test shows it's a touch device you can use this to apply styles. This will rarely be used in the CSS. But might be handy in the JavaScript early on in the code flow. */

}

html.touch-device {

/* Here you add the styles that only the touch devices should use. Try to avoid it as much as possible. */

}

This is what a real example would like in your stylesheet

/* This will not affect touch devices */
html.no-touch-device a:hover {
    font-weight: bold;
}

/* This will not affect touch devices */

html.no-touch-device a:hover {

font-weight: bold;

}

Try a live example here:

See the Pen WbKbaN by Jon WAllsten (@JonWallsten) on CodePen.

When I was working as a frontend developer for a retailer, developing a web shop, I stumbled upon a tricky problem.
My customer was pretty picky, and didn’t want any edge case flaws.

We had a fixed (or sticky of you supported that) navigation that was always attached from top to bottom.
The nav did only cover about 2/3 of the screen’s width though, so when the user reached the end of the content,
you could see how the background started scrolling instead. The scrolling was leaking upwards to the body.

Note: This has been fixed in iOS 8 but is still a valid defect in iOS 7 and below, as well as Android.

To fix this you need to listen to the touchstart and touchmove events and check where you are in the content and which direction you are scrolling.
When you have reached the bottom of the container and the direction you are scrolling is downwards we simple use preventDefault() to stop the scroll event,
to avoid it leaking to the body content.

The wrapper covers the whole screen so when user scrolls outside of the menu, it will still scroll the menu.
It’s using a semi-transparent color to appear modular.

The content covers the width of the menu.

I also need to mention that this solution is not perfect on Android devices.
If you scroll almost all the way to the bottom, and then scrolling past the bottom without lifting you finger, the scroll will leak with the following error message in the console:

Ignored attempt to cancel a touchmove event with cancelable=false, for example because scrolling is in progress and cannot be interrupted.

A way around this, is to implement a custom scroll like iScroll, this is what we ended up doing, although not optimal, of course.

Here’s the JavaScript fixing the problem, I have explained the code with comments inside the script itself.

$leftNavWrap = $('.leftNavWrapper');
$leftNavContent = $('.leftNavContent');

var enableFix = function () {
  var scrolling = false, ts = null;
  
//Attach a listener to touchstart so we can get the direction
  $(document).on('touchstart.scrollable', $leftNavWrap, function (e) {
    if (!scrolling) {
      scrolling = true;
      
      //If we're at the top we move the scroll 1 pixel to "unlock" it.
      if (e.currentTarget.scrollTop === 0) {
        e.currentTarget.scrollTop = 1;
      } else if (e.currentTarget.scrollHeight === e.currentTarget.scrollTop + e.currentTarget.offsetHeight) {
        e.currentTarget.scrollTop -= 1;
      }
      scrolling = false;
    }
     
    //Save touch event so we can compare it with the next event
    ts = e.originalEvent.touches[0].clientY;
  });

  //Attach a touchmove listener where we calculate the direction and stop the scrolling if necessary 
  $(document).on('touchmove.scrollable', $leftNavWrap, function (e) {
    //Get the touch event and compare it with our previous touchstart event. 
    //If the current clientY is greater than the previous one we're moving downwards, otherwise upwards.
    var te = e.originalEvent.changedTouches[0].clientY, 
        direction = ts > te ? 'down' : 'up';

    //Specify wrapper and container
    $container = $leftNavWrap;
    $content = $leftNavContent;
   
    if ($content.height() <= $container.height()) {
      //If wrapper height is greater than content height we always prevent the scrolling
      e.preventDefault();
    } else if ($container.scrollTop() <= 1 && direction == 'up') {
      //If user has scrolled all the way to the top and the direction is up, we prevent the scroll.
      e.preventDefault();
    } else if ($container.scrollTop() > 0 && $container.scrollTop() + $container.height() >= $content.height() - 1 && direction == 'down') {
      //If user has scrolled all the way to the bottom and the direction is down we also prevent the scroll.
      e.preventDefault();
    }
  });
 }

$leftNavWrap = $('.leftNavWrapper');

$leftNavContent = $('.leftNavContent');

var enableFix = function () {

var scrolling = false, ts = null;

//Attach a listener to touchstart so we can get the direction

$(document).on('touchstart.scrollable', $leftNavWrap, function (e) {

if (!scrolling) {

scrolling = true;

//If we're at the top we move the scroll 1 pixel to "unlock" it.

if (e.currentTarget.scrollTop === 0) {

e.currentTarget.scrollTop = 1;

} else if (e.currentTarget.scrollHeight === e.currentTarget.scrollTop + e.currentTarget.offsetHeight) {

e.currentTarget.scrollTop -= 1;

}

scrolling = false;

}

//Save touch event so we can compare it with the next event

ts = e.originalEvent.touches[0].clientY;

});

//Attach a touchmove listener where we calculate the direction and stop the scrolling if necessary

$(document).on('touchmove.scrollable', $leftNavWrap, function (e) {

//Get the touch event and compare it with our previous touchstart event.

//If the current clientY is greater than the previous one we're moving downwards, otherwise upwards.

var te = e.originalEvent.changedTouches[0].clientY,

direction = ts > te ? 'down' : 'up';

//Specify wrapper and container

$container = $leftNavWrap;

$content = $leftNavContent;

if ($content.height() <= $container.height()) {

//If wrapper height is greater than content height we always prevent the scrolling

e.preventDefault();

} else if ($container.scrollTop() <= 1 && direction == 'up') {

//If user has scrolled all the way to the top and the direction is up, we prevent the scroll.

e.preventDefault();

} else if ($container.scrollTop() > 0 && $container.scrollTop() + $container.height() >= $content.height() - 1 && direction == 'down') {

//If user has scrolled all the way to the bottom and the direction is down we also prevent the scroll.

e.preventDefault();

}

});

}

Try it out on your device:
https://jonwallsten.com/codepen-examples/example1/

See the Pen RNMrmP by Jon WAllsten (@JonWallsten) on CodePen.

Category: Tips & Tricks

How to handle hover on touch devices in simple way [JavaScript + CSS]

How to avoid scroll leakage when scrolling a fixed menu on touch devices