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How to animate a progress bar with negatives using Element.animate()

I'm attempting to mimic the following widget with HTML/CSS/JavaScript:
https://gyazo.com/76bee875d35b571bd08edbe73ead12cb
The way that I have it set up is the following:
I have a bar with a background color that has a gradient from red to green which is static.
I then have two blinders that is supposed to represent the negative space to give the illusion that the colored bars are animating (in reality, the blinders are simply sliding away)
I did it this way because I figured it might be easier instead of trying to animate the bar going in both directions, but now I'm not so sure lol. One requirement that I'm trying to keep is that the animation only deals with transform or opacity to take advantage of optimizations the browser can do (as described here: https://hacks.mozilla.org/2016/08/animating-like-you-just-dont-care-with-element-animate/)
The example has a few buttons to help test various things. The "Random positive" works great, and is exactly what I want. I haven't quite hooked up the negative yet tho because I'm not sure how to approach the problem of transitioning from positive to negative and vice-versa.
Ideally, when going from a positive to a negative, the right blinder will finish at the middle, and the left blinder will pick up the animation and finish off where it needs to go.
So for example, if the values is initially set to 40%, and the then set to -30%, the right blinder should animate transform: translateX(40%) -> transform: translateX(0%) and then the left blinder should animate from transform: translateX(0%) -> transform: translateX(-30%) to expose the red.
Also, the easing should be seamless.
I'm not sure if this is possible with the setup (specifically keeping the easing seamless, since the easing would be per-element, I think, and can't "carry over" to another element?)
Looking for guidance on how I can salvage this to produce the expected results, or if there's a better way to deal with this.
Note: I'm using jquery simply for ease with click events and whatnot, but this will eventually be in an application that's not jquery aware.
Here's my current attempt: https://codepen.io/blitzmann/pen/vYLrqEW
let currentPercentageState = 0;
function animate(percentage) {
var animation = [{
transform: `translateX(${currentPercentageState}%)`,
easing: "ease-out"
},
{
transform: `translateX(${percentage}%)`
}
];
var timing = {
fill: "forwards",
duration: 1000
};
$(".blind.right")[0].animate(animation, timing);
// save the new value so that the next iteration has a proper from keyframe
currentPercentageState = percentage;
}
$(document).ready(function() {
$(".apply").click(function() {
animate($("#amount").val());
});
$(".reset").click(function() {
animate(0);
});
$(".random").click(function() {
var val = (Math.random() * 2 - 1) * 100;
$("#amount").val(val);
animate(val);
});
$(".randomPos").click(function() {
var val = Math.random() * 100;
$("#amount").val(val);
animate(val);
});
$(".randomNeg").click(function() {
var val = Math.random() * -100;
$("#amount").val(val);
animate(val);
});
$(".toggleBlinds").click(function() {
$(".blind").toggle();
});
$(".toggleLeft").click(function() {
$(".blind.left").toggle();
});
$(".toggleRight").click(function() {
$(".blind.right").toggle();
});
});
$(document).ready(function() {});
.wrapper {
margin: 10px;
height: 10px;
width: 800px;
background: linear-gradient(to right, red 50%, green 50%);
border: 1px solid black;
box-sizing: border-box;
position: relative;
overflow: hidden;
}
.blind {
height: 100%;
position: absolute;
top: 0;
background-color: rgb(51, 51, 51);
min-width: 50%;
}
.blind.right {
left: 50%;
border-left: 1px solid white;
transform-origin: left top;
}
.blind.left {
border-right: 1px solid white;
transform-origin: left top;
}
<div class="wrapper">
<div class='blind right'></div>
<div class='blind left'></div>
</div>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.0/jquery.min.js" type="text/javascript"></script>
<input id="amount" type="number" placeholder="Enter percentage..." value='40' />
<button class="apply">Apply</button>
<button class="random">Random</button>
<button class="randomPos">Random Positive</button>
<button class="randomNeg">Random Negative</button>
<button class="toggleBlinds">Toggle Blinds</button>
<button class="toggleLeft">Toggle L Blind</button>
<button class="toggleRight">Toggle R Blind</button>
<button class="reset" href="#">Reset</button>

I've modified your code. Have a look at the code.
let currentPercentageState = 0;
function animate(percentage) {
var animation = [{
transform: `translateX(${currentPercentageState}%)`,
easing: "ease-out"
},
{
transform: `translateX(${percentage}%)`
}
];
var timing = {
fill: "forwards",
duration: 1000
};
if (percentage < 0) {
$(".blind.right")[0].animate(
[{
transform: `translateX(0%)`,
easing: "ease-out"
},
{
transform: `translateX(0%)`
}
], timing);
$(".blind.left")[0].animate(animation, timing);
} else {
$(".blind.left")[0].animate(
[{
transform: `translateX(0%)`,
easing: "ease-out"
},
{
transform: `translateX(0%)`
}
], timing);
$(".blind.right")[0].animate(animation, timing);
}
// save the new value so that the next iteration has a proper from keyframe
//currentPercentageState = percentage;
}
$(document).ready(function() {
$(".apply").click(function() {
animate($("#amount").val());
});
$(".reset").click(function() {
animate(0);
});
$(".random").click(function() {
var val = (Math.random() * 2 - 1) * 100;
$("#amount").val(val);
animate(val);
});
$(".randomPos").click(function() {
var val = Math.random() * 100;
$("#amount").val(val);
animate(val);
});
$(".randomNeg").click(function() {
var val = Math.random() * -100;
$("#amount").val(val);
animate(val);
});
$(".toggleBlinds").click(function() {
$(".blind").toggle();
});
$(".toggleLeft").click(function() {
$(".blind.left").toggle();
});
$(".toggleRight").click(function() {
$(".blind.right").toggle();
});
});
$(document).ready(function() {});
.wrapper {
margin: 10px;
height: 10px;
width: 800px;
background: linear-gradient(to right, red 50%, green 50%);
border: 1px solid black;
box-sizing: border-box;
position: relative;
overflow: hidden;
}
.blind {
height: 100%;
position: absolute;
top: 0;
background-color: rgb(51, 51, 51);
min-width: 50%;
}
.blind.right {
left: 50%;
border-left: 1px solid white;
transform-origin: left top;
}
.blind.left {
border-right: 1px solid white;
transform-origin: left top;
}
<div class="wrapper">
<div class='blind right'></div>
<div class='blind left'></div>
</div>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.0/jquery.min.js" type="text/javascript"></script>
<input id="amount" type="number" placeholder="Enter percentage..." value='40' />
<button class="apply">Apply</button>
<button class="random">Random</button>
<button class="randomPos">Random Positive</button>
<button class="randomNeg">Random Negative</button>
<button class="toggleBlinds">Toggle Blinds</button>
<button class="toggleLeft">Toggle L Blind</button>
<button class="toggleRight">Toggle R Blind</button>
<button class="reset" href="#">Reset</button>

You need to animate the things in two steps. The first step is to reset the previous state to initial state(which should be set to 0) and in the second step, you need to run the other animation which will actually move it to the destination state.
In order to achive this you can do,
let currentPercentageState = 0;
const animationTiming = 300;
function animate(percentage) {
let defaultTranformVal = [{
transform: `translateX(${currentPercentageState}%)`,
easing: "ease-out"
}, {transform: `translateX(0%)`}];
var animation = [{
transform: `translateX(0%)`,
easing: "ease-out"
},{
transform: `translateX(${percentage}%)`,
easing: "ease-out"
}];
var timing = {
fill: "forwards",
duration: animationTiming
};
if (percentage < 0) {
if(currentPercentageState > 0) {
$(".blind.right")[0].animate(defaultTranformVal, timing);
setTimeout(() => {
$(".blind.left")[0].animate(animation, timing);
}, animationTiming);
} else {
$(".blind.left")[0].animate(animation, timing);
}
}
if(percentage > 0) {
if(currentPercentageState < 0) {
$(".blind.left")[0].animate(defaultTranformVal, timing);
setTimeout(() => {
$(".blind.right")[0].animate(animation, timing);
}, animationTiming);
} else {
$(".blind.right")[0].animate(animation, timing);
}
}
// save the new value so that the next iteration has a proper from keyframe
currentPercentageState = percentage;
}
Here, you will see we have two transformations. The first one defaultTranformVal will move the currentPercentageState to zero and then the other one which will move from 0 to percentage.
You need to handle a couple of conditions here. The first one is if you are running it the first time(means there is no currentPercentageState), you don't need to run defaultTranformVal. If you have currentPercentageState then you need to run defaultTranformVal and then run the second animation.
Note:- You also need to clear the timeout in order to prevent the memory leak. This can be handle by storing the setTimout return value and then when next time it's running clear the previous one with the help of clearTimeout.
Here is the updated codepen example:-
https://codepen.io/gauravsoni119/pen/yLeZBmb?editors=0011

EDIT: I actually did manage to solve this!
let easing = "cubic-bezier(0.5, 1, 0.89, 1)";
let duration = 1000;
let easeReversal = y => 1 - Math.sqrt((y-1)/-1)
https://codepen.io/blitzmann/pen/WNrBWpG
I gave it my own cubic-bezier function of which I know the reversal for. The post below and my explanation was based on an easing function using sin() which isn't easily reversible. Not only that, but the built in easing function for ease-out doesn't match the sin() one that I had a reference for (I'm not really sure what the build in one is based on). But I realized I could give it my own function that I knew the reversal for, and boom, works like a charm!
This has been a very informative experience for me, I'm glad that I've got a solution that works. I still think I'll dip my toes in the other ideas that I had to see which pans out better in the long term.
Historical post:
So, after a few nights of banging my head around on this, I've come to the conclusion that this either isn't possible the way I was thinking about doing it, or if it is possible then the solution is so contrived that it's probably not worth it and I'd be better off developing a new solution (of which I've thought of one or tow things that I'd like to try).
Please see this jsfiddle for my final "solution" and a post-mortem
https://jsfiddle.net/blitzmann/zc80p1n4/
let currentPercentageState = 0;
let easing = "linear";
let duration = 1000;
function animate(percentage) {
percentage = parseFloat(percentage);
// determine if we've crossed the 0 threshold, which would force us to do something else here
let threshold = currentPercentageState / percentage < 0;
console.log("Crosses 0: " + threshold);
if (!threshold && percentage != 0) {
// determine which blind we're animating
let blind = percentage < 0 ? "left" : "right";
$(`.blind.${blind}`)[0].animate(
[
{
transform: `translateX(${currentPercentageState}%)`,
easing: easing
},
{
transform: `translateX(${percentage}%)`
}
],
{
fill: "forwards",
duration: duration
}
);
} else {
// this happens when we cross the 0 boundry
// we'll have to create two animations - one for moving the currently offset blind back to 0, and then another to move the second blind
let firstBlind = percentage < 0 ? "right" : "left";
let secondBlind = percentage < 0 ? "left" : "right";
// get total travel distance
let delta = currentPercentageState - percentage;
// find the percentage of that travel that the first blind is responsible for
let firstTravel = currentPercentageState / delta;
let secondTravel = 1 - firstTravel;
console.log("delta; total values to travel: ", delta);
console.log(
"firstTravel; percentage of the total travel that should be done by the first blind: ",
firstTravel
);
console.log(
"secondTravel; percentage of the total travel that should be done by the second blind: ",
secondTravel
);
// animate the first blind.
$(`.blind.${firstBlind}`)[0].animate(
[
{
transform: `translateX(${currentPercentageState}%)`,
easing: easing
},
{
// we go towards the target value instead of 0 since we'll cut the animation short
transform: `translateX(${percentage}%)`
}
],
{
fill: "forwards",
duration: duration,
// cut the animation short, this should run the animation to this x value of the easing function
iterations: firstTravel
}
);
// animate the second blind
$(`.blind.${secondBlind}`)[0].animate(
[
{
transform: `translateX(${currentPercentageState}%)`,
easing: easing
},
{
transform: `translateX(${percentage}%)`
}
],
{
fill: "forwards",
duration: duration,
// start the iteration where the first should have left off. This should put up where the easing function left off
iterationStart: firstTravel,
// we only need to carry this aniamtion the rest of the way
iterations: 1-firstTravel,
// delay this animation until the first "meets" it
delay: duration * firstTravel
}
);
}
// save the new value so that the next iteration has a proper from keyframe
currentPercentageState = percentage;
}
// the following are just binding set ups for the buttons
$(document).ready(function () {
$(".apply").click(function () {
animate($("#amount").val());
});
$(".reset").click(function () {
animate(0);
});
$(".random").click(function () {
var val = (Math.random() * 2 - 1) * 100;
$("#amount").val(val);
animate(val);
});
$(".randomPos").click(function () {
var val = Math.random() * 100;
$("#amount").val(val);
animate(val);
});
$(".randomNeg").click(function () {
var val = Math.random() * -100;
$("#amount").val(val);
animate(val);
});
$(".flipSign").click(function () {
animate(currentPercentageState * -1);
});
$(".toggleBlinds").click(function () {
$(".blind").toggle();
});
$(".toggleLeft").click(function () {
$(".blind.left").toggle();
});
$(".toggleRight").click(function () {
$(".blind.right").toggle();
});
});
animate(50);
//setTimeout(()=>animate(-100), 1050)
$(function () {
// Build "dynamic" rulers by adding items
$(".ruler[data-items]").each(function () {
var ruler = $(this).empty(),
len = Number(ruler.attr("data-items")) || 0,
item = $(document.createElement("li")),
i;
for (i = -11; i < len - 11; i++) {
ruler.append(item.clone().text(i + 1));
}
});
// Change the spacing programatically
function changeRulerSpacing(spacing) {
$(".ruler")
.css("padding-right", spacing)
.find("li")
.css("padding-left", spacing);
}
changeRulerSpacing("30px");
});
.wrapper {
margin: 10px auto 2px;
height: 10px;
width: 600px;
background: linear-gradient(to right, red 50%, green 50%);
border: 1px solid black;
box-sizing: border-box;
position: relative;
overflow: hidden;
}
.blind {
height: 100%;
position: absolute;
top: 0;
background-color: rgb(51, 51, 51);
min-width: 50%;
}
.blind.right {
left: 50%;
border-left: 1px solid white;
transform-origin: left top;
}
.blind.left {
border-right: 1px solid white;
transform-origin: left top;
}
#buttons {
text-align: center;
}
/* Ruler crap */
.ruler-container {
text-align: center;
}
.ruler, .ruler li {
margin: 0;
padding: 0;
list-style: none;
display: inline-block;
}
/* IE6-7 Fix */
.ruler, .ruler li {
*display: inline;
}
.ruler {
display:inline-block;
margin: 0 auto;https://jsfiddle.net/user/login/
background: lightYellow;
box-shadow: 0 -1px 1em hsl(60, 60%, 84%) inset;
border-radius: 2px;
border: 1px solid #ccc;
color: #ccc;
height: 3em;
padding-right: 1cm;
white-space: nowrap;
margin-left: 1px;
}
.ruler li {
padding-left: 1cm;
width: 2em;
margin: .64em -1em -.64em;
text-align: center;
position: relative;
text-shadow: 1px 1px hsl(60, 60%, 84%);
}
.ruler li:before {
content: '';
position: absolute;
border-left: 1px solid #ccc;
height: .64em;
top: -.64em;
right: 1em;
}
<div class="wrapper">
<div class='blind right'></div>
<div class='blind left'></div>
</div>
<div class="ruler-container">
<ul class="ruler" data-items="21"></ul>
</div>
<div id="buttons">
<input id="amount" type="number" placeholder="Enter percentage..." value='-80' />
<button class="apply">Apply</button>
<button class="random">Random</button>
<button class="randomPos">Random Positive</button>
<button class="randomNeg">Random Negative</button>
<button class="flipSign">Flip Sign</button>
<button class="toggleBlinds">Toggle Blinds</button>
<button class="toggleLeft">Toggle L Blind</button>
<button class="toggleRight">Toggle R Blind</button>
<button class="reset" href="#">Reset</button>
</div>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.0/jquery.min.js" type="text/javascript"></script>
<hr />
<p><strong>A note</strong> on the attempt made here:</p>
<p>
I was trying to animate a percentage bar that has both positive and negative values. But I set a challenge as well: I wanted to achieve this via animations utilizing only the compositor - which means animating opacity or transform <strong>only</strong> (no color, width, height, position, etc). The ideas presented here were based on the concept of blinds. I have a static element with a background gradient of red to green, then I have two elements that "blind" the user to the background. These blinds, being a simple element, simply slide into and out of place.
</p>
<p>The problem that I ran into was timing the two animations correctly when they switched signage. It's currently working (very well) for linear animation, but as soon as you introduce an easing function it gets wonky. The reason for this is due to the value that I'm using to set the first animation length (iteration, not duration), as well as the second animations start to pick up where the first left off. The value that I was using is the percentage of the total travel distance that each of the blinds will have to do.</p>
<p>So, for example, if you have a value of 50, and go to -80, that's a total travel distance of 130. The first blind travels <code>50 / 130 = ~0.3846</code> of the total distance, and the second blind will travel <code>1 - ~0.3846 = ~0.6154</code> of the total distance.</p>
<p>But, these are not the correct values for the <em>duration</em> of the animation. Instead, these are the percentages of the easing values (the y-axis). To get the duration for these, I would have to find the x value (given the known y value). eg, for an ease-out animation for a value going from 50 to -80, the animation crosses our 0 at ~0.03846, and we would have to solve for x given <code>0.03846 = sin((x * PI) / 2)</code>.</p>
<p>With the help of Wolfram Alpha, I was able to find a few test values this got me much closer to the actual animation, but the blinds always stopped slightly off the mark. I eventually chalked this up to one of two reasons: the fact that the valuess are always going to be approximate and the browser is never going to be 100% accurate, or / and 2) the browser is using a slightly different easing function than I was using for reference. Regardless, being so constrained by the fact that this "animation" relies on two different aniamtions lining up perfectly, I decided to leave this version be and go in a different direction.</p>
<p>
If anyone finds an actual solution to this, please post an answer here: https://stackoverflow.com/questions/62866844/how-to-animate-a-progress-bar-with-negatives-using-element-animate
</p>
Thanks to those that attempted this admittedly tricky problem

Trying to display comments near appropriate doc range in Vue component

I am attempting to emulate Medium style comments in an html document.
This answer has gotten me nearly there: How to implement Medium-style commenting interface in VueJS
With that method, I can highlight text and make comments, but I want to display the coments on the same line as the range the commenter selected. The code as I have treats every paragraph it seems as a separate document, such that I don't know how to return to the correct paragraph to find the original range being commented on.
Here is the commenting component:
<template>
<div class="popup" :style="{top: offsetTop, left: offsetLeft}" ref="popup">
<span #click="AlertSelectedText">Comment</span>
</div>
</template>
<script>
export default {
data() {
return {
popupInitialTopOffset: 0,
popupInitialLeftOffset: 0,
offsetTop: 0,
offsetLeft: "-999em",
selectedText: undefined
};
},
methods: {
ListenToDocumentSelection() {
let sel = window.getSelection();
console.log('sel is: ', sel)
setTimeout(_ => {
if (sel && !sel.isCollapsed) {
this.selectedText = sel.toString();
if (sel.rangeCount) {
let range = sel.getRangeAt(0).cloneRange();
console.log('range is: ', range)
if (range.getBoundingClientRect) {
var rect = range.getBoundingClientRect();
console.log('boundingrect is: ', rect)
let left = rect.left + (rect.right - rect.left) / 2;
let top = rect.top;
this.offsetTop = top - this.popupInitialTopOffset - 30 + "px";
this.offsetLeft = left - this.popupInitialLeftOffset / 2 + "px";
}
}
} else {
this.offsetLeft = "-999em";
}
}, 0);
},
AlertSelectedText() {
alert(`"${this.selectedText}" posted as comment`);
}
},
mounted() {
this.popupInitialTopOffset = this.$refs.popup.offsetHeight;
this.popupInitialLeftOffset = this.$refs.popup.offsetWidth;
console.log('this is the positions of the popup', this.popupInitialTopOffset, this.popupInitialLeftOffset);
window.addEventListener("mouseup", this.ListenToDocumentSelection);
},
destroyed() {
window.removeEventListener("mouseup", this.ListenToDocumentSelection);
}
};
</script>
<style scoped>
.popup {
position: absolute;
color: #FFF;
background-color: #000;
padding: 10px;
border-radius: 5px;
transform-origin: center, center;
cursor: pointer;
}
.popup:after {
content: "";
border-bottom: 5px solid #000;
border-right: 5px solid #000;
border-top: 5px solid transparent;
border-left: 5px solid transparent;
position: absolute;
top: calc(100% - 5px);
transform: rotate(45deg);
left: calc(50% - 3px);
}
</style>
if I could know how to add coordinates for returning to the commented range, I think I could manage the rest.

Wherever you want to enable commenting, try giving those elements a class and a unique ID.
A class would help you identify that it has commenting enabled whereas an ID would help you uniquely identify it.
In your logic, you can access the list of classes on that element as
sel.anchorNode.parentElement.classList
and ID as
sel.anchorNode.parentElement.id
With the help of this combination, you can surely associate a comment to your elements.

CSS Scroll Snap Points with navigation (next, previous) buttons

I am building a carousel, very minimalist, using CSS snap points. It is important for me to have CSS only options, but I'm fine with enhancing a bit with javascript (no framework).
I am trying to add previous and next buttons to scroll programmatically to the next or previous element. If javascript is disabled, buttons will be hidden and carousel still functionnal.
My issue is about how to trigger the scroll to the next snap point ?
All items have different size, and most solution I found require pixel value (like scrollBy used in the exemple). A scrollBy 40px works for page 2, but not for others since they are too big (size based on viewport).
function goPrecious() {
document.getElementById('container').scrollBy({
top: -40,
behavior: 'smooth'
});
}
function goNext() {
document.getElementById('container').scrollBy({
top: 40,
behavior: 'smooth'
});
}
#container {
scroll-snap-type: y mandatory;
overflow-y: scroll;
border: 2px solid var(--gs0);
border-radius: 8px;
height: 60vh;
}
#container div {
scroll-snap-align: start;
display: flex;
justify-content: center;
align-items: center;
font-size: 4rem;
}
#container div:nth-child(1) {
background: hotpink;
color: white;
height: 50vh;
}
#container div:nth-child(2) {
background: azure;
height: 40vh;
}
#container div:nth-child(3) {
background: blanchedalmond;
height: 60vh;
}
#container div:nth-child(4) {
background: lightcoral;
color: white;
height: 40vh;
}
<div id="container">
<div>1</div>
<div>2</div>
<div>3</div>
<div>4</div>
</div>
<button onClick="goPrecious()">previous</button>
<button onClick="goNext()">next</button>

Nice question! I took this as a challenge.
So, I increased JavaScript for it to work dynamically. Follow my detailed solution (in the end the complete code):
First, add position: relative to the .container, because it need to be reference for scroll and height checkings inside .container.
Then, let's create 3 global auxiliary variables:
1) One to get items scroll positions (top and bottom) as arrays into an array. Example: [[0, 125], [125, 280], [280, 360]] (3 items in this case).
3) One that stores half of .container height (it will be useful later).
2) Another one to store the item index for scroll position
var carouselPositions;
var halfContainer;
var currentItem;
Now, a function called getCarouselPositions that creates the array with items positions (stored in carouselPositions) and calculates the half of .container (stored in halfContainer):
function getCarouselPositions() {
carouselPositions = [];
document.querySelectorAll('#container div').forEach(function(div) {
carouselPositions.push([div.offsetTop, div.offsetTop + div.offsetHeight]); // add to array the positions information
})
halfContainer = document.querySelector('#container').offsetHeight/2;
}
getCarouselPositions(); // call it once
Let's replace the functions on buttons. Now, when you click on them, the same function will be called, but with "next" or "previous" argument:
<button onClick="goCarousel('previous')">previous</button>
<button onClick="goCarousel('next')">next</button>
Here is about the goCarousel function itself:
First, it creates 2 variables that store top scroll position and bottom scroll position of carousel.
Then, there are 2 conditionals to see if the current carousel position is on most top or most bottom.
If it's on top and clicked "next" button, it will go to the second item position. If it's on bottom and clicked "previous" button, it will go the previous one before the last item.
If both conditionals failed, it means the current item is not the first or the last one. So, it checks to see what is the current position, calculating using the half of the container in a loop with the array of positions to see what item is showing. Then, it combines with "previous" or "next" checking to set the correct next position for currentItem variable.
Finally, it goes to the correct position through scrollTo using currentItem new value.
Below, the complete code:
var carouselPositions;
var halfContainer;
var currentItem;
function getCarouselPositions() {
carouselPositions = [];
document.querySelectorAll('#container div').forEach(function(div) {
carouselPositions.push([div.offsetTop, div.offsetTop + div.offsetHeight]); // add to array the positions information
})
halfContainer = document.querySelector('#container').offsetHeight/2;
}
getCarouselPositions(); // call it once
function goCarousel(direction) {
var currentScrollTop = document.querySelector('#container').scrollTop;
var currentScrollBottom = currentScrollTop + document.querySelector('#container').offsetHeight;
if (currentScrollTop === 0 && direction === 'next') {
currentItem = 1;
} else if (currentScrollBottom === document.querySelector('#container').scrollHeight && direction === 'previous') {
console.log('here')
currentItem = carouselPositions.length - 2;
} else {
var currentMiddlePosition = currentScrollTop + halfContainer;
for (var i = 0; i < carouselPositions.length; i++) {
if (currentMiddlePosition > carouselPositions[i][0] && currentMiddlePosition < carouselPositions[i][1]) {
currentItem = i;
if (direction === 'next') {
currentItem++;
} else if (direction === 'previous') {
currentItem--
}
}
}
}
document.getElementById('container').scrollTo({
top: carouselPositions[currentItem][0],
behavior: 'smooth'
});
}
window.addEventListener('resize', getCarouselPositions);
#container {
scroll-snap-type: y mandatory;
overflow-y: scroll;
border: 2px solid var(--gs0);
border-radius: 8px;
height: 60vh;
position: relative;
}
#container div {
scroll-snap-align: start;
display: flex;
justify-content: center;
align-items: center;
font-size: 4rem;
}
#container div:nth-child(1) {
background: hotpink;
color: white;
height: 50vh;
}
#container div:nth-child(2) {
background: azure;
height: 40vh;
}
#container div:nth-child(3) {
background: blanchedalmond;
height: 60vh;
}
#container div:nth-child(4) {
background: lightcoral;
color: white;
height: 40vh;
}
<div id="container">
<div>1</div>
<div>2</div>
<div>3</div>
<div>4</div>
</div>
<button onClick="goCarousel('previous')">previous</button>
<button onClick="goCarousel('next')">next</button>
Another good detail to add is to call getCarouselPositions function again if the window resizes:
window.addEventListener('resize', getCarouselPositions);
That's it.
That was cool to do. I hope it can help somehow.

I've just done something similar recently. The idea is to use IntersectionObserver to keep track of which item is in view currently and then hook up the previous/next buttons to event handler calling Element.scrollIntoView().
Anyway, Safari does not currently support scroll behavior options. So you might want to polyfill it on demand with polyfill.app service.
let activeIndex = 0;
const container = document.querySelector("#container");
const elements = [...document.querySelectorAll("#container div")];
function handleIntersect(entries){
const entry = entries.find(e => e.isIntersecting);
if (entry) {
const index = elements.findIndex(
e => e === entry.target
);
activeIndex = index;
}
}
const observer = new IntersectionObserver(handleIntersect, {
root: container,
rootMargin: "0px",
threshold: 0.75
});
elements.forEach(el => {
observer.observe(el);
});
function goPrevious() {
if(activeIndex > 0) {
elements[activeIndex - 1].scrollIntoView({
behavior: 'smooth'
})
}
}
function goNext() {
if(activeIndex < elements.length - 1) {
elements[activeIndex + 1].scrollIntoView({
behavior: 'smooth'
})
}
}
#container {
scroll-snap-type: y mandatory;
overflow-y: scroll;
border: 2px solid var(--gs0);
border-radius: 8px;
height: 60vh;
}
#container div {
scroll-snap-align: start;
display: flex;
justify-content: center;
align-items: center;
font-size: 4rem;
}
#container div:nth-child(1) {
background: hotpink;
color: white;
height: 50vh;
}
#container div:nth-child(2) {
background: azure;
height: 40vh;
}
#container div:nth-child(3) {
background: blanchedalmond;
height: 60vh;
}
#container div:nth-child(4) {
background: lightcoral;
color: white;
height: 40vh;
}
<div id="container">
<div>1</div>
<div>2</div>
<div>3</div>
<div>4</div>
</div>
<button onClick="goPrevious()">previous</button>
<button onClick="goNext()">next</button>

An easier approach done with react.
export const AppCarousel = props => {
const containerRef = useRef(null);
const carouselRef = useRef(null);
const [state, setState] = useState({
scroller: null,
itemWidth: 0,
isPrevHidden: true,
isNextHidden: false
})
const next = () => {
state.scroller.scrollBy({left: state.itemWidth * 3, top: 0, behavior: 'smooth'});
// Hide if is the last item
setState({...state, isNextHidden: true, isPrevHidden: false});
}
const prev = () => {
state.scroller.scrollBy({left: -state.itemWidth * 3, top: 0, behavior: 'smooth'});
setState({...state, isNextHidden: false, isPrevHidden: true});
// Hide if is the last item
// Show remaining
}
useEffect(() => {
const items = containerRef.current.childNodes;
const scroller = containerRef.current;
const itemWidth = containerRef.current.firstElementChild?.clientWidth;
setState({...state, scroller, itemWidth});
return () => {
}
},[props.items])
return (<div className="app-carousel" ref={carouselRef}>
<div className="carousel-items shop-products products-swiper" ref={containerRef}>
{props.children}
</div>
<div className="app-carousel--navigation">
<button className="btn prev" onClick={e => prev()} hidden={state.isPrevHidden}><</button>
<button className="btn next" onClick={e => next()} hidden={state.isNextHidden}>></button>
</div>
</div>)
}

I was struggling with the too while working with a react project and came up with this solution. Here's a super basic example of the code using react and styled-components.
import React, { useState, useRef } from 'react';
import styled from 'styled-components';
const App = () => {
const ref = useRef();
const [scrollX, setScrollX] = useState(0);
const scrollSideways = (px) => {
ref.current.scrollTo({
top: 0,
left: scrollX + px,
behavior: 'smooth'
});
setScrollX(scrollX + px);
};
return (
<div>
<List ref={ref}>
<ListItem color="red">Card 1</ListItem>
<ListItem color="blue">Card 2</ListItem>
<ListItem color="green">Card 3</ListItem>
<ListItem color="yellow">Card 4</ListItem>
</List>
<button onClick={() => scrollSideways(-600)}> Left </button>
<button onClick={() => scrollSideways(600)}> Right </button>
</div>
);
};
const List = styled.ul`
display: flex;
overflow-x: auto;
padding-inline-start: 40px;
scroll-snap-type: x mandatory;
list-style: none;
padding: 40px;
width: 700px;
`;
const ListItem = styled.li`
display: flex;
flex-shrink: 0;
scroll-snap-align: start;
background: ${(p) => p.color};
width: 600px;
margin-left: 15px;
height: 200px;
`;

display 3 items in carousel - used existing pen

I found a pen online to create image carousel, problem is I can't get it display 3 items inside a container.
I have tried removing the opacity for the carousel photo but then it messes up the display for the full container.
Here is link to my fiddle:
!(function(d) {
// Variables to target our base class, get carousel items, count how many carousel items there are, set the slide to 0 (which is the number that tells us the frame we're on), and set motion to true which disables interactivity.
var itemClassName = "carousel__photo";
items = d.getElementsByClassName(itemClassName),
totalItems = items.length,
slide = 0,
moving = false;
// To initialise the carousel we'll want to update the DOM with our own classes
function setInitialClasses() {
// Target the last, initial, and next items and give them the relevant class.
// This assumes there are three or more items.
items[totalItems - 1].classList.add("prev");
items[0].classList.add("active");
items[1].classList.add("next");
}
// Set click events to navigation buttons
function setEventListeners() {
var next = d.getElementsByClassName('carousel__button--next')[0],
prev = d.getElementsByClassName('carousel__button--prev')[0];
next.addEventListener('click', moveNext);
prev.addEventListener('click', movePrev);
}
// Disable interaction by setting 'moving' to true for the same duration as our transition (0.5s = 500ms)
function disableInteraction() {
moving = true;
setTimeout(function() {
moving = false
}, 500);
}
function moveCarouselTo(slide) {
// Check if carousel is moving, if not, allow interaction
if (!moving) {
// temporarily disable interactivity
disableInteraction();
// Preemptively set variables for the current next and previous slide, as well as the potential next or previous slide.
var newPrevious = slide - 1,
newNext = slide + 1,
oldPrevious = slide - 2,
oldNext = slide + 2;
// Test if carousel has more than three items
if ((totalItems - 1) > 3) {
// Checks if the new potential slide is out of bounds and sets slide numbers
if (newPrevious <= 0) {
oldPrevious = (totalItems - 1);
} else if (newNext >= (totalItems - 1)) {
oldNext = 0;
}
// Check if current slide is at the beginning or end and sets slide numbers
if (slide === 0) {
newPrevious = (totalItems - 1);
oldPrevious = (totalItems - 2);
oldNext = (slide + 1);
} else if (slide === (totalItems - 1)) {
newPrevious = (slide - 1);
newNext = 0;
oldNext = 1;
}
// Now we've worked out where we are and where we're going, by adding and removing classes, we'll be triggering the carousel's transitions.
// Based on the current slide, reset to default classes.
items[oldPrevious].className = itemClassName;
items[oldNext].className = itemClassName;
// Add the new classes
items[newPrevious].className = itemClassName + " prev";
items[slide].className = itemClassName + " active";
items[newNext].className = itemClassName + " next";
}
}
}
// Next navigation handler
function moveNext() {
// Check if moving
if (!moving) {
// If it's the last slide, reset to 0, else +1
if (slide === (totalItems - 1)) {
slide = 0;
} else {
slide++;
}
// Move carousel to updated slide
moveCarouselTo(slide);
}
}
// Previous navigation handler
function movePrev() {
// Check if moving
if (!moving) {
// If it's the first slide, set as the last slide, else -1
if (slide === 0) {
slide = (totalItems - 1);
} else {
slide--;
}
// Move carousel to updated slide
moveCarouselTo(slide);
}
}
// Initialise carousel
function initCarousel() {
setInitialClasses();
setEventListeners();
// Set moving to false now that the carousel is ready
moving = false;
}
// make it rain
initCarousel();
}(document));
/* Parent wrapper to carousel. Width can be changed as needed. */
.carousel-wrapper {
overflow: hidden;
width: 90%;
margin: auto;
}
.carousel-custom-section {
width: 100%;
display: flex;
}
.carousel-single-item {
width: 33%;
display: flex;
}
.carousel-single-item-row {
display: flex;
width: 33%;
flex-direction: row;
}
.carousel-wrapper * {
box-sizing: border-box;
}
.carousel {
-webkit-transform-style: preserve-3d;
-moz-transform-style: preserve-3d;
transform-style: preserve-3d;
}
.carousel__photo {
opacity: 0;
position: absolute;
top: 0;
width: 100%;
margin: auto;
padding: 1rem 4rem;
z-index: 100;
/* transition: transform .5s, opacity .5s, z-index .5s; */
}
.carousel__photo.initial,
.carousel__photo.active {
opacity: 1;
position: relative;
z-index: 900;
}
.carousel__photo.prev,
.carousel__photo.next {
z-index: 800;
}
/* Style navigation buttons to sit in the middle, either side of the carousel. */
.carousel__button--prev,
.carousel__button--next {
position: absolute;
top: 50%;
width: 3rem;
height: 3rem;
background-color: #FFF;
transform: translateY(-50%);
border-radius: 50%;
cursor: pointer;
z-index: 1001;
}
.carousel__button--prev {
left: 0;
}
.carousel__button--next {
right: 0;
}
/* Use pseudo elements to insert arrows inside of navigation buttons */
.carousel__button--prev::after,
.carousel__button--next::after {
content: " ";
position: absolute;
width: 10px;
height: 10px;
top: 50%;
left: 54%;
border-right: 2px solid black;
border-bottom: 2px solid black;
transform: translate(-50%, -50%) rotate(135deg);
}
.carousel__button--next::after {
left: 47%;
transform: translate(-50%, -50%) rotate(-45deg);
}
<div class="carousel-wrapper">
<div class="carousel">
<div class="carousel-custom-section">
<div class="carousel-single-item">
<img class="carousel__photo initial" src="https://via.placeholder.com/150/0000FF/808080?text=one">
</div>
<div class="carousel-single-item">
<img class="carousel__photo" src="https://via.placeholder.com/150/FF0000/808080?text=two">
</div>
<div class="carousel-single-item">
<img class="carousel__photo" src="https://via.placeholder.com/150/00FF00/808080?text=three">
</div>
</div>
<div class="carousel-custom-section">
<div class="carousel-single-item">
<img class="carousel__photo" src="https://via.placeholder.com/150/FF0000/808080?text=four">
</div>
<div class="carousel-single-item">
<img class="carousel__photo" src="https://via.placeholder.com/150/00FF00/808080?text=five">
</div>
<div class="carousel-single-item">
<img class="carousel__photo" src="https://via.placeholder.com/150/00FF00/808080?text=six">
</div>
</div>
<div class="carousel__button--next"></div>
<div class="carousel__button--prev"></div>
</div>
</div>
Can somebody please point me in right direction what I am doing wrong?

How to run the Callback function inside of the prototype in JavaScript?

According to this question and mdn.doc articles, I'm giving a Callback function inside of aprototype for managing the next code line after it's done.
But even if I create the Callback, the browser keeps ignoring it and running the next code line no matter the Callback is completed or not.
This is the code:
'use strict';
(function() {
function Box($el, $frame) {
// Reassign the Values
this.$el = $el;
this.$frame = $frame;
// Event Register Zone
this.$el.addEventListener('touchstart', (e) => this.start(e));
this.$el.addEventListener('touchmove', (e) => this.move(e));
this.$el.addEventListener('touchend', (e) => this.end(e));
}
Box.prototype = {
start: function(e) {
console.log('touchstart has been detected');
},
move: function(e) {
console.log('touchmove has been detected');
},
end: function(e) {
console.log('touchend has been detected');
this.getanAction(this.moveTop);
},
getanAction: function(callback) {
let bound = callback.bind(this);
bound();
this.$frame[1].classList.add('leftMover');
// Expectation: move the purple box first, and move the orange box next
},
moveTop: function() {
this.$frame[0].classList.add('topMover');
}
}
/***************************************************************/
// Declare & Assign the Original Values
let _elem = document.getElementById('box');
let _frame = _elem.querySelectorAll('.contents');
const proBox = new Box(_elem, _frame);
}());
* {
margin: 0;
padding: 0;
}
#box {
width: auto;
height: 800px;
border: 4px dotted black;
}
.contents {
position: absolute;
width: 200px;
height: 200px;
float: left;
top: 0;
left: 0;
transition: 800ms cubic-bezier(0.455, 0.03, 0.515, 0.955);
}
.purple { background-color: purple; }
.orange { background-color: orange; }
.topMover { top: 600px; }
.leftMover { left: 600px; }
<div id="box">
<div class="contents purple">
</div>
<div class="contents orange">
</div>
</div>
My expectation is the .orange box moves after the .purple box moves done.
Did I miss or do something wrong from the code?

The problem is they are being called one after the other with no delay as JavaScript won't wait for the CSS transition to finish before moving to the next line.
I've fixed waiting for the first transition has finished before calling the bound callback. This way the purple box will move, wait for the transition to finish, then the orange box will move.
'use strict';
(function() {
function Box($el, $frame) {
// Reassign the Values
this.$el = $el;
this.$frame = $frame;
// Event Register Zone
this.$el.addEventListener('touchstart', (e) => this.start(e));
this.$el.addEventListener('touchmove', (e) => this.move(e));
// Added mouse up so it works on desktop
this.$el.addEventListener('mouseup', (e) => this.end(e));
this.$el.addEventListener('touchend', (e) => this.end(e));
}
Box.prototype = {
start: function(e) {
console.log('touchstart has been detected');
},
move: function(e) {
console.log('touchmove has been detected');
},
end: function(e) {
console.log('touchend has been detected');
this.getanAction(this.moveTop);
},
getanAction: function(callback) {
let bound = callback.bind(this);
// Listen for css transition end
this.$frame[0].addEventListener('transitionend', function() {
// Call callback to move orange box
bound()
});
// Move the purple box now
this.$frame[0].classList.add('topMover1')
},
moveTop: function() {
this.$frame[1].classList.add('topMover2');
}
}
/***************************************************************/
// Declare & Assign the Original Values
let _elem = document.getElementById('box');
let _frame = _elem.querySelectorAll('.contents');
const proBox = new Box(_elem, _frame);
}());
* {
margin: 0;
padding: 0;
}
#box {
width: auto;
height: 800px;
border: 4px dotted black;
}
.contents {
position: absolute;
width: 200px;
height: 200px;
float: left;
top: 0;
left: 0;
transition: 800ms cubic-bezier(0.455, 0.03, 0.515, 0.955);
}
.purple { background-color: purple; }
.orange { background-color: orange; }
.topMover1 { top: 600px; }
.topMover2 { left: 600px; }
<div id="box">
<div class="contents purple">
</div>
<div class="contents orange">
</div>
</div>