Assume 6 absolute positioned HTML elements stacked one on top of the other, A-F, with "A" on top.
<body data-swipe-threshold="100">
<div><img alt = "F"/></div>
<div><img alt = "E"/></div>
<div><img alt = "D"/></div>
<div><img alt = "C"/></div>
<div><img alt = "B"/></div>
<div><img alt = "A"/></div>
</body>
For touch-enabled screens I want the user to be able to swipe to the right over the "A" div/image to place it on the bottom of the stack (exposing "B"). The next right-swipe exposing "C", etc. Conversely, a swipe left should bring the "card" on the bottom of the deck to the top, where it becomes visible. I would allow "F" to expose "A" with a right-swipe when "F" is on top, and also allow "A" to expose "F" with a left swipe. I realize I'll be manipulating zIndex, but I seem unable to capture/process a swipe event with elements stacked in this way. "swiped-events.js" is the script I am using. My code is here: https://jsfiddle.net/okrcmLw5/ but even when I test outside of "fiddle" the demo seems to ignore my swipes. Thanks!
swiped-events.js creates an event when the user swipes. It does this on the element at which the touchstart event was seen, and it looks for touchstart events on the whole document.
Putting an event listener on the deck element receives the 'swipe' event but the target of the event seems to be the contained img element. So we cannot use event.target to find the whole swiped div, but it's the whole swiped div we want to move.
If we do not try to do things with z-index but instead use the JS prepend and appendChild functions we can move the top element to the bottom or vice versa without worrying about which of the div's child elements (there is only one at the moment, but there is no reason there could not be several, a caption for instance) has been swiped.
Here's the JS to do this:
document.getElementById('deck').addEventListener('swiped-left', function () { deck.appendChild(deck.firstElementChild); });
document.getElementById('deck').addEventListener('swiped-right', function () { deck.prepend(deck.lastElementChild); });
and here is a snippet. It includes all the js code from github.com/john-doherty/swiped-event in case that gets moved/deleted. Snippet tested on touch device - iPad with IOS14.2 - and on Edge dev tools 'emulator'.
/*!
* swiped-events.js - v@version@
* Pure JavaScript swipe events
* https://github.com/john-doherty/swiped-events
* @inspiration https://stackoverflow.com/questions/16348031/disable-scrolling-when-touch-moving-certain-element
* @author John Doherty <www.johndoherty.info>
* @license MIT
*/
function init() {
'use strict';
// patch CustomEvent to allow constructor creation (IE/Chrome)
if (typeof window.CustomEvent !== 'function') {
window.CustomEvent = function (event, params) {
params = params || { bubbles: false, cancelable: false, detail: undefined };
var evt = document.createEvent('CustomEvent');
evt.initCustomEvent(event, params.bubbles, params.cancelable, params.detail);
return evt;
};
window.CustomEvent.prototype = window.Event.prototype;
}
document.addEventListener('touchstart', handleTouchStart, false);
document.addEventListener('touchmove', handleTouchMove, false);
document.addEventListener('touchend', handleTouchEnd, false);
var xDown = null;
var yDown = null;
var xDiff = null;
var yDiff = null;
var timeDown = null;
var startEl = null;
/**
* Fires swiped event if swipe detected on touchend
* @param {object} e - browser event object
* @returns {void}
*/
function handleTouchEnd(e) {
// if the user released on a different target, cancel!
// !!THIS NEVER HAPPENS AT LEAST ON SAFARI IPAD IOS 14.2, IF RELEASE OUTSIDE THE START ELEMENT IT GIVES THE TARGET AS THE START ELEMENT
if (startEl !== e.target) { return;}
var swipeThreshold = parseInt(getNearestAttribute(startEl, 'data-swipe-threshold', '20'), 10); // default 20px
var swipeTimeout = parseInt(getNearestAttribute(startEl, 'data-swipe-timeout', '500'), 10); // default 500ms
var timeDiff = Date.now() - timeDown;
var eventType = '';
var changedTouches = e.changedTouches || e.touches || [];
if (Math.abs(xDiff) > Math.abs(yDiff)) { // most significant
if (Math.abs(xDiff) > swipeThreshold && timeDiff < swipeTimeout) {
if (xDiff > 0) {
eventType = 'swiped-left';
}
else {
eventType = 'swiped-right';
}
}
}
else if (Math.abs(yDiff) > swipeThreshold && timeDiff < swipeTimeout) {
if (yDiff > 0) {
eventType = 'swiped-up';
}
else {
eventType = 'swiped-down';
}
}
if (eventType !== '') {
var eventData = {
dir: eventType.replace(/swiped-/, ''),
xStart: parseInt(xDown, 10),
xEnd: parseInt((changedTouches[0] || {}).clientX || -1, 10),
yStart: parseInt(yDown, 10),
yEnd: parseInt((changedTouches[0] || {}).clientY || -1, 10)
};
// fire `swiped` event event on the element that started the swipe
startEl.dispatchEvent(new CustomEvent('swiped', { bubbles: true, cancelable: true, detail: eventData }));
// fire `swiped-dir` event on the element that started the swipe
startEl.dispatchEvent(new CustomEvent(eventType, { bubbles: true, cancelable: true, detail: eventData }));
}
// reset values
xDown = null;
yDown = null;
timeDown = null;
}
/**
* Records current location on touchstart event
* @param {object} e - browser event object
* @returns {void}
*/
function handleTouchStart(e) {
// if the element has data-swipe-ignore="true" we stop listening for swipe events
if (e.target.getAttribute('data-swipe-ignore') === 'true') return;
startEl = e.target;
timeDown = Date.now();
xDown = e.touches[0].clientX;
yDown = e.touches[0].clientY;
xDiff = 0;
yDiff = 0;
}
/**
* Records location diff in px on touchmove event
* @param {object} e - browser event object
* @returns {void}
*/
function handleTouchMove(e) {
if (!xDown || !yDown) return;
var xUp = e.touches[0].clientX;
var yUp = e.touches[0].clientY;
xDiff = xDown - xUp;
yDiff = yDown - yUp;
}
/**
* Gets attribute off HTML element or nearest parent
* @param {object} el - HTML element to retrieve attribute from
* @param {string} attributeName - name of the attribute
* @param {any} defaultValue - default value to return if no match found
* @returns {any} attribute value or defaultValue
*/
function getNearestAttribute(el, attributeName, defaultValue) {
// walk up the dom tree looking for data-action and data-trigger
while (el && el !== document.documentElement) {
var attributeValue = el.getAttribute(attributeName);
if (attributeValue) {
return attributeValue;
}
el = el.parentNode;
}
return defaultValue;
}
}
document.getElementById('deck').addEventListener('swiped-left', function () { deck.appendChild(deck.firstElementChild); });
document.getElementById('deck').addEventListener('swiped-right', function () { deck.prepend(deck.lastElementChild); });
init(); body { overflow: hidden; padding: 100px; }
#deck {
position: relative;
}
#deck > div {
position: absolute;
top: 0;
left: 0;
}<div id="deck" data-swipe-threshold="100">
<div><img src="http://dummyimage.com/250x250/000/fff&text=F" /></div>
<div><img src="http://dummyimage.com/250x250/000/fff&text=E" /></div>
<div><img src="http://dummyimage.com/250x250/000/fff&text=D" /></div>
<div><img src="http://dummyimage.com/250x250/000/fff&text=C" /></div>
<div><img src="http://dummyimage.com/250x250/000/fff&text=B" /></div>
<div><img src="http://dummyimage.com/250x250/000/fff&text=A" /></div>
</div>