Develop Reference

Fade in text letter by letter based on scroll

I'm having problems with a functionality that I have to implement, I'm looking to do this (check the second section) -> https://www.jacquemus.com/fr/simon
The letters need to fade in and fade out, based on the scroll, this is what I got so far
<div class="ml3">
<h1>THIS IS MY TEXT THAT IT'S GOING TO SHOW IN SCROLL</h1>
</div>
:root {
--percentage: 0;
}
body {
background-color: #000;
margin: 0;
height: 120vh;
}
.ml3 {
position: sticky;
top: 0;
height: 100vh;
display: flex;
justify-content: center;
align-items: center;
}
span {
font-family: Helvetica;
margin: 0;
padding: 0;
font-size: 48px;
color: #fff;
letter-spacing: -0.3px;
}
.ml3 span{
opacity: var(--percentage);
}
var textWrapper = document.querySelector('.ml3');
textWrapper.innerHTML = textWrapper.textContent.replace(/\S/g, "<span class='letter'>$&</span>");
var letter = document.querySelectorAll('.letter');
var i = 0;
var currentID = 0;
var slideCount = letter.length;
document.addEventListener('scroll', (e) => {
let scrolled = document.documentElement.scrollTop / (document.documentElement.scrollHeight - document.documentElement.clientHeight);
var nextID = currentID + 1;
if(nextID < slideCount){
letter[nextID].style.setProperty('--percentage', `${scrolled / 1}` * nextID);
}
currentID = nextID;
});
https://codepen.io/federicomartin/pen/eYdBbQm
As you can see, it's no near what I want, but I really don't know how to do it, if someone could help me, would be awesome! Thanks!

I like that effect a lot!! Thank for submitting that question! ;)
So here is a something to help you continue on this challenge.
In the scroll handler, I replaced:
var nextID = currentID + 1;
if(nextID < slideCount){
letter[nextID].style.setProperty('--percentage', `${scrolled / 1}` * nextID);
}
currentID = nextID;
with:
letter.forEach(function (l, i) {
if (i / letter.length < scrolled) {
l.style.setProperty("--percentage", 1);
}else{
l.style.setProperty("--percentage", 0);
}
});
It compares the scrolled percentage you calculated with the letter index "percentage" in the letter collection to set it's opacity to 0 or 1.
I would then adjust the scrollHeight of the body with the real text to reveal... Below, I used height: 600vh; and may be a bit too much. ;)
var textWrapper = document.querySelector(".ml3");
textWrapper.innerHTML = textWrapper.textContent.replace(
/\S/g,
"<span class='letter'>$&</span>"
);
var letter = document.querySelectorAll(".letter");
var i = 0;
var currentID = 0;
var slideCount = letter.length;
document.addEventListener("scroll", (e) => {
let scrolled =
document.documentElement.scrollTop /
(document.documentElement.scrollHeight -
document.documentElement.clientHeight);
// var nextID = currentID + 1;
// if (nextID < slideCount) {
// letter[nextID].style.setProperty(
// "--percentage",
// `${scrolled / 1}` * nextID
// );
// }
// currentID = nextID;
letter.forEach(function (l, i) {
// console.log("====",i / letter.length, i, letter.length)
if (i / letter.length < scrolled) {
l.style.setProperty("--percentage", 1);
} else {
l.style.setProperty("--percentage", 0);
}
});
});
:root {
--percentage: 0;
}
body {
background-color: #000;
margin: 0;
height: 1120vh;
}
.ml3 {
position: sticky;
top: 0;
height: 100vh;
display: flex;
justify-content: center;
align-items: center;
}
span {
font-family: Helvetica;
margin: 0;
padding: 0;
font-size: 48px;
color: #fff;
letter-spacing: -0.3px;
}
.ml3 span {
opacity: var(--percentage);
}
<div class="ml3">
<h1>THIS IS MY TEXT THAT IT'S GOING TO SHOW IN SCROLL</h1>
</div>
CodePen

How to clear previous data in an infinite scroll

I have coded an infinite scroll. When the user scrolls it will load an additional 20 items which makes it a long list.
I want the scroll to loads new items and clear the previous items.
var listElm = document.querySelector('#infinite-list');
// Add 20 items.
var nextItem = 1;
var loadMore = function() {
for (var i = 0; i < 20; i++) {
var item = document.createElement('li');
item.innerText = 'Item ' + nextItem++;
listElm.appendChild(item);
}
}
// Detect when scrolled to bottom.
listElm.addEventListener('scroll', function() {
if (listElm.scrollTop + listElm.clientHeight >= listElm.scrollHeight) {
loadMore();
}
});
// Initially load some items.
loadMore();
#infinite-list {
/* We need to limit the height and show a scrollbar */
width: 200px;
height: 300px;
overflow: auto;
/* Optional, only to check that it works with margin/padding */
margin: 30px;
padding: 20px;
border: 10px solid black;
}
/* Optional eye candy below: */
li {
padding: 10px;
list-style-type: none;
}
li:hover {
background: #ccc;
}
<ul id='infinite-list'>
</ul>

If you empty the list before that, would it be ok?
var listElm = document.querySelector('#infinite-list');
// Add 20 items.
var nextItem = 1;
var loadMore = function() {
listElm.innerHTML = ''
for (var i = 0; i < 20; i++) {
var item = document.createElement('li');
item.innerText = 'Item ' + nextItem++;
listElm.appendChild(item);
}
}
// Detect when scrolled to bottom.
listElm.addEventListener('scroll', function() {
if (listElm.scrollTop + listElm.clientHeight >= listElm.scrollHeight ) {
loadMore();
}
});
// Initially load some items.
loadMore();
#infinite-list {
/* We need to limit the height and show a scrollbar */
width: 200px;
height: 300px;
overflow: auto;
/* Optional, only to check that it works with margin/padding */
margin: 30px;
padding: 20px;
border: 10px solid black;
}
/* Optional eye candy below: */
li {
padding: 10px;
list-style-type: none;
}
li:hover {
background: #ccc;
}
<ul id='infinite-list'>
</ul>

You can empty the list every time loadMore() is called.
var listElm = document.querySelector('#infinite-list');
// Add 20 items.
var nextItem = 1;
var loadMore = function() {
//Here we empty the list to remove the old results
listElm.innerHTML = ''
//And then load the new items
for (var i = 0; i < 20; i++) {
var item = document.createElement('li');
item.innerText = 'Item ' + nextItem++;
listElm.appendChild(item);
}
}
// Detect when scrolled to bottom.
listElm.addEventListener('scroll', function() {
if (listElm.scrollTop + listElm.clientHeight >= listElm.scrollHeight ) {
loadMore();
}
});
// Initially load some items.
loadMore();

How to sort elements on DOM by its inner Text

I have a graph that is rendering its values as a div inside the body element with a class according to their number values. This is working fine. But next I need to sort the divs according to their number values or background color. BUT, it needs to start on the lower left corner of the page and fan out upwards to towards the right as the numbers increase. Basically just like a line graph.
I'd like to stay away from libraries if at all possible.
How would I approach this? Thank you all.
let interval = setInterval(makeDivs, 5);
function makeDivs(){
let cont = checkHeight();
if(cont){
let div = document.createElement('div');
let randNum = Math.random() * 100;
if(randNum < 20) { div.classList.add('blue') }
if(randNum >= 20 && randNum < 40) { div.classList.add('green') }
if(randNum >= 40 && randNum < 60) { div.classList.add('yellow') }
if(randNum >= 60 && randNum < 80) { div.classList.add('orange') }
if(randNum >= 80 && randNum < 101) { div.classList.add('red') }
div.textContent = randNum.toFixed(2);
document.querySelector('body').appendChild(div);
} else {
alert('done');
clearInterval(interval);
sortDivs(); // Begin sorting divs
}
}
function checkHeight(){
let w = window.innerHeight;
let b = document.querySelector('body').offsetHeight;
if(b < w) {
return true;
} else {
return false;
}
}
function sortDivs(){
document.querySelector("body div:last-child").remove();
alert('sorting now...')
}
* { box-sizing: border-box;}
body { width: 100vw; margin: 0; padding: 0; display: flex; flex-wrap: wrap; align-items: end;}
body div { width: calc(10% + 1px); text-align: center; border: 1px solid #ddd; margin: -1px 0 0 -1px; padding: 10px;}
body div.blue { background: aqua; }
body div.green { background: green; }
body div.yellow { background: yellow; }
body div.orange { background: orange; }
body div.red { background: red; }
UPDATE!!!
So I have this so far based on the feed back down below. The problem now is the sorting is only happening laterally and not on an angle (spreading right and to the top).
let interval = setInterval(makeDivs, 10);
function makeDivs(){
let cont = checkHeight();
if(cont){
let div = document.createElement('div');
let randNum = Math.random() * 100;
if(randNum < 20) { div.classList.add('blue') }
if(randNum >= 20 && randNum < 40) { div.classList.add('green') }
if(randNum >= 40 && randNum < 60) { div.classList.add('yellow') }
if(randNum >= 60 && randNum < 80) { div.classList.add('orange') }
if(randNum >= 80 && randNum < 101) { div.classList.add('red') }
div.textContent = randNum.toFixed(2);
document.querySelector('.outPut').appendChild(div);
} else {
clearInterval(interval);
document.querySelector(".outPut div:last-child").remove();
compileArrays(); // Begin sorting divs
}
}
function checkHeight(){
let w = window.innerHeight;
let b = document.querySelector('.outPut').offsetHeight;
if(b < w) {
return true;
} else {
return false;
}
}
function compileArrays(){
let divs = document.querySelectorAll('.outPut div');
let bArr = [], gArr = [], yArr = [], oArr = [], rArr = [];
divs.forEach( (d) => {
if( d.classList.contains('blue') ){ bArr.push(d) }
if( d.classList.contains('green') ){ gArr.push(d) }
if( d.classList.contains('yellow') ){ yArr.push(d) }
if( d.classList.contains('orange') ){ oArr.push(d) }
if( d.classList.contains('red') ){ rArr.push(d) }
});
let finalArr = sortArray(bArr).concat(sortArray(gArr)).concat(sortArray(yArr)).concat(sortArray(oArr)).concat(sortArray(rArr));
newDom(finalArr);
}
function sortArray(arr){
let newArr = arr;
newArr.sort( (a, b) => {
return a.innerText - b.innerText;
});
return newArr;
}
function newDom(arr){
let b = document.querySelector('.outPut');
b.innerHTML = '';
arr.reverse();
arr.forEach((a) => {
b.appendChild(a);
});
}
* { box-sizing: border-box;}
body { width: 100vw; height: 100vh; margin: 0; padding: 0; display: flex; align-items: flex-end;}
body .outPut { flex: 1; display: flex; flex-wrap: wrap; flex-direction:row-reverse; }
body .outPut div { width: calc(10% + 1px); text-align: center; border: 1px solid #ddd; margin: -1px 0 0 -1px; padding: 10px;}
body .outPut div.blue { background: aqua; }
body .outPut div.green { background: #44df15; }
body .outPut div.yellow { background: yellow; }
body .outPut div.orange { background: orange; }
body .outPut div.red { background: red; }
<div class="outPut"></div>

Supposed you already have a mechanism to organise such DIVs in a grid as shown, the following should give you what you are looking for:
var items = divList.filter((div) => div.nodeType == 1); // get rid of the whitespace text nodes
items.sort(function(a, b) {
return a.innerHTML == b.innerHTML
? 0
: (a.innerHTML > b.innerHTML ? 1 : -1);
});
Then, place them back in the DOM as needed, example:
for (i = 0; i < items.length; ++i) {
divList.appendChild(items[i]);
}

This worked with the first code example!!!
try this sortDivs function:
function sortDivs() {
document.querySelector("body div:last-child").remove();
alert('sorting now...')
let toSort = document.getElementsByTagName("div")
toSort = Array.prototype.slice.call(toSort, 0)
toSort.sort((a, b) => {
let aord = parseFloat(a.textContent);
let bord = parseFloat(b.textContent);
return bord - aord;
})
document.body.innerHTML = ""
for(var i = 0, l = toSort.length; i < l; i++) {
document.querySelector('body').appendChild(toSort[i]);
}
}
and in the css file set flex-wrap to wrap-reverse. Hope I could help :)
PS: please, implement some else if instead of doing only if

Here is a small fiddle with my sample code demonstrating a simple solution in pure JavaScript and absolute CSS positioning for what you are trying to achieve. Link
As some pointed out already, there might be a library, that already provides a better and complete solution for this - I did not research if it is so.
Code:
file.js
var container = document.getElementById("container")
var results = [1,2,3,4,5,6,7,8]
//you can pre-calculate the order of the distances
//here already orderdered array [distanec][X-axis][Y-axis]
var distances =[[0,0,0],
[1,1,0],
[1,0,1],
[1.414, 1,1],
[2,0,2],
[2,2,0],
[2.234, 2,1],
[2.234, 1,2]]
for (i = 0; i < results.length; i++){
var newDiv = document.createElement("div")
newDiv.className = "result"
newDiv.innerHTML = results[i]
newDiv.style.left = distances[i][1]*20 + "px"
newDiv.style.bottom = distances[i][2]*20 + "px"
container.appendChild(newDiv)
}
function setColor(element){
// set class based on value - you already have this part
}
style.css
#container {
border: 4px;
border-color: red;
border-style: solid;
height: 200px;
width: 200px;
position: relative;
}
.result{
border: 2px;
width: 20px;
height: 20px;
position: absolute;
border-color: blue;
border-style: solid;
text-align: center;
}
site.html
<div id="container">
</div>
Output:

Math.random duplicates numbers JavaScript

I want to randomly assign a class at two boxes.
But even with indexOf(randomIndex) === -1) Math.random is duplicating the numbers.
If you refresh you will see that the boxes are changing classes but sometimes they both have the same class, this should happened.
var grid = document.getElementById("grid-box");
for (var i = 0; i <= 1; i++) {
var square = document.createElement("div");
square.className = 'square';
square.id = 'square' + i;
grid.appendChild(square);
}
var weaponTwo = [];
while (weaponTwo.length < 1) {
var randomIndex = parseInt(2 * Math.random());
if (weaponTwo.indexOf(randomIndex) === -1) {
weaponTwo.push(randomIndex);
var drawWtwo = document.getElementById('square' + randomIndex);
$(drawWtwo).addClass("w2")
}
};
var weapon3 = [];
while (weapon3.length < 1) {
var randomIndex = parseInt(2 * Math.random());
if (weapon3.indexOf(randomIndex) === -1) {
weapon3.push(randomIndex);
var draw3 = document.getElementById('square' + randomIndex);
$(draw3).addClass("w3")
}
};
#grid-box {
width: 420px;
height: 220px;
}
#grid-box>div.square {
font-size: 1rem;
vertical-align: top;
display: inline-block;
width: 10%;
height: 10%;
box-sizing: border-box;
border: 1px solid #000;
}
.w2 {
background-color: red;
}
.w3 {
background-color: blue;
}
<script src="https://code.jquery.com/jquery-1.12.4.js"></script>
<div id="grid-box"></div>

You are using two different arrays for storing the weapons. Use same array so that the number is not repeated.
var grid = document.getElementById("grid-box");
for (var i = 0; i <= 1; i++) {
var square = document.createElement("div");
square.className = 'square';
square.id = 'square' + i;
grid.appendChild(square);
}
var weaponTwo = [];
while (weaponTwo.length < 1) {
var randomIndex = parseInt(2 * Math.random());
if (weaponTwo.indexOf(randomIndex) === -1) {
weaponTwo.push(randomIndex);
var drawWtwo = document.getElementById('square' + randomIndex);
$(drawWtwo).addClass("w2")
}
};
while (weaponTwo.length < 2) {
var randomIndex = parseInt(2 * Math.random());
if (weaponTwo.indexOf(randomIndex) === -1) {
weaponTwo.push(randomIndex);
var draw3 = document.getElementById('square' + randomIndex);
$(draw3).addClass("w3")
}
};
#grid-box {
width: 420px;
height: 220px;
}
#grid-box>div.square {
font-size: 1rem;
vertical-align: top;
display: inline-block;
width: 10%;
height: 10%;
box-sizing: border-box;
border: 1px solid #000;
}
.w2 {
background-color: red;
}
.w3 {
background-color: blue;
}
<script src="https://code.jquery.com/jquery-1.12.4.js"></script>
<div id="grid-box"></div>
Better Approach : You can create an array of classes and then shuffle it using this alogrithm. Then you can pop from the array and add to classes one by one.

Background Image Shouldn't Appear In Header In Drop Down Menu

I've made a JavaScript dropdown menu. Everything works fine, except the background image. I have the image set to change when the dropdown menu is expanded, which also works fine.
The issue is with the headers. Unless the header is set to display inline-block or inline, the menu won't expand. When set to inline-block or inline everything expands when you click on the box. But if you click on the header itself, it adds the padding and border around the header and ads in the background image from the div. How do you prevent this from happening?
<div class="panel">
<div class="collapse"><h2>Features</h2></div>
<div class="elements">
text<br>text<br>text
</div>
</div>
<style>
h2 {/*display: inline-block;*/
/*display: inline;*/
margin: 0px;
padding: 0px 0px 0px 0px;
color: #ffffff;
text-align: center;
text-transform: uppercase;}
.expand,
.collapse {cursor: pointer;
background-position: center right;
background-repeat: no-repeat;
background-color: #000033;
border: 2px solid #990044;
color: #ffffff;
padding: 10px 0px;
text-align: center;}
.collapse {background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABwAAAAcCAYAAAByDd+UAAABHUlEQVRIS+3USw6CMBAA0BYNutOjcAQ9iXHjhoXhBt4AEmwwbvQm6g04ii4hCLaNNRUp/dDgQllRPvMy05lC0PMFe/bAH7Re8R8qaYySTZGPoyBYXm3WMQwP04Gbhfd8FJDYtKTxNjkCCBf4Ni3y0dwWSrChm51wXI/FhjHaRXix5rKygtYwGr4C1QUitPdKUJ7xemILbcJw7JsDnBktqU20DfP9VfoaCxuoDCPJvc1hF1QF+wBNy6uKNYK6qA4mBFVRXawVlKHkPTfUbKJo65NuFJ1W0sNb1EjPgOQEUcakGbJIApRPQpoZ+1iaoQKqjCln2IJqYdpgrZGArEGaGke5pPzPZE/Juq0bjbtU9KPpc6MMTTGjPeyCfQV8AK4c2lwJRjQ3AAAAAElFTkSuQmCC);}
.expand {background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABwAAAAcCAYAAAByDd+UAAABD0lEQVRIS+3Wyw2CQBAG4F1Q8KadSAnYgR0YL164SCWYKDHxonZgB1ICdiI3QR6yCgSVXXaAkGDkwgXyZf6dYcCo5Qu37KFugIaxH5FkdH1+hSYErpBgPck9E8j35AkUBYE5TEkqs6EoN1iApWmCUC6QgYHRUpCCOYk0zDUNV6VMkIYJSFAJFKLQim8glAqyME1b2AQ0zZ0CRQtBHiyNEop+gRCsCvoGVsGgaAbWwSDoE2wC40VxkxgPiteb7QFhPMsNsEPmLG196DZgolF0fFXYd614M47jhxvBCtEIXfy7rGZnKEq3k4jEZd3KPhMhcxqgYBV4gylZZaXf0qqR0t77g00n2pG/tjpl/37TPACe/d8VUJ3+EgAAAABJRU5ErkJggg==);}
.elements {background-color: #ccd9ff;
overflow: hidden;}
</style>
<script>
function aaManageEvent (eventObj, event, eventHandler) {
if (eventObj.addEventListener) {eventObj.addEventListener (event, eventHandler, false);}
else if (eventObj.attachEvent) {event = "on" + event; eventObj.attachEvent (event, eventHandler);}
}
window.onload = function () {
var divs = document.getElementsByTagName ("div");
for (var i = 0; i < divs.length; i++) {
if (divs[i].className == "collapse") {
aaManageEvent (divs [i], "click", spring.expandOrCollapse);
}
else if (divs[i].className == "elements") {
var height = divs [i].offsetHeight;
divs [i] .height = height;
if (divs [i] .id == "") divs [i].id = "div" + i;
divs [i].style.height = "0";
}
}
}
var spring = {
// adjust height
adjustItem : function (val, newItem) {
document.getElementById (newItem).style.height = val + "px";
},
// check if expand or collapse
expandOrCollapse : function (evnt) {
evnt = evnt ? evnt : window.event;
var target = evnt.target ? evnt.target : evnt.srcElement;
if (target.className == "collapse") spring.expand (target);
else spring.collapse (target);
},
// Expand Panel
expand : function (target) {
target.className = 'expand';
var children = target.parentNode.childNodes, panel;
for (var i = 0; i < children.length; i++) {
if (children [i].className == "elements") {
panel = children [i]; break;
}
}
var height = panel.height, incr = height / 20;
for (var i=0; i < 20; i++) {
var val = (i + 1) * incr;
var func = "spring.adjustItem (" + val + ", '" + panel.id + "')";
setTimeout (func, (i + 1) * 30);
}
},
// Collapse Panel
collapse : function (target) {
target.className = "collapse";
var children = target.parentNode.childNodes, panel;
for (var i = 0; i < children.length; i++) {
if (children [i].className == "elements") {
panel = children [i]; break;
}
}
var height = panel.height, decr = height / 20;
for (var i = 0; i < 20; i++) {
var val = height - (decr * (i + 1));;
var func = "spring.adjustItem (" + val + ", '" + panel.id + "')";
setTimeout (func, (i + 1) * 30);
}
}
};
</script>

When I click on the div, the dropdown works. But when I click on the header, I see an error in the browser console.
I think because when clicking on the <h2>Features</h2> element, the click event bubbles up to the <div class="collapse">, making the var target in this line not the <div class="collapse"> but the <h2>:
var target = evnt.target ? evnt.target : evnt.srcElement;
A possible solution to fix this is for example to add an id to this line:
<div id="header" class="collapse"><h2>Features</h2></div>
Then you can directly get that div by id and change the classname.
I've adjusted your expandOrCollapse function to make it toggle based on the classname from the div with id="header".
For example:
function aaManageEvent (eventObj, event, eventHandler) {
if (eventObj.addEventListener) {eventObj.addEventListener (event, eventHandler, false);}
else if (eventObj.attachEvent) {event = "on" + event; eventObj.attachEvent (event, eventHandler);}
}
window.onload = function () {
var divs = document.getElementsByTagName ("div");
for (var i = 0; i < divs.length; i++) {
if (divs[i].className == "collapse") {
aaManageEvent (divs [i], "click", spring.expandOrCollapse);
}
else if (divs[i].className == "elements") {
var height = divs [i].offsetHeight;
divs [i] .height = height;
if (divs [i] .id == "") divs [i].id = "div" + i;
divs [i].style.height = "0";
}
}
}
var spring = {
// adjust height
adjustItem : function (val, newItem) {
document.getElementById (newItem).style.height = val + "px";
},
// check if expand or collapse
expandOrCollapse : function (evnt) {
var header = document.getElementById('header');
if (header.className === "collapse") {
spring.expand(header);
} else {
spring.collapse(header);
}
},
// Expand Panel
expand : function (target) {
target.className = 'expand';
var children = target.parentNode.childNodes, panel;
for (var i = 0; i < children.length; i++) {
if (children [i].className == "elements") {
panel = children [i]; break;
}
}
var height = panel.height, incr = height / 20;
for (var i=0; i < 20; i++) {
var val = (i + 1) * incr;
var func = "spring.adjustItem (" + val + ", '" + panel.id + "')";
setTimeout (func, (i + 1) * 30);
}
},
// Collapse Panel
collapse : function (target) {
target.className = "collapse";
var children = target.parentNode.childNodes, panel;
for (var i = 0; i < children.length; i++) {
if (children [i].className == "elements") {
panel = children [i]; break;
}
}
var height = panel.height, decr = height / 20;
for (var i = 0; i < 20; i++) {
var val = height - (decr * (i + 1));;
var func = "spring.adjustItem (" + val + ", '" + panel.id + "')";
setTimeout (func, (i + 1) * 30);
}
}
};
h2 {/*display: inline-block;*/
/*display: inline;*/
margin: 0px;
padding: 0px 0px 0px 0px;
color: #ffffff;
text-align: center;
text-transform: uppercase;}
.expand,
.collapse {cursor: pointer;
background-position: center right;
background-repeat: no-repeat;
background-color: #000033;
border: 2px solid #990044;
color: #ffffff;
padding: 10px 0px;
text-align: center;}
.collapse {background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABwAAAAcCAYAAAByDd+UAAABHUlEQVRIS+3USw6CMBAA0BYNutOjcAQ9iXHjhoXhBt4AEmwwbvQm6g04ii4hCLaNNRUp/dDgQllRPvMy05lC0PMFe/bAH7Re8R8qaYySTZGPoyBYXm3WMQwP04Gbhfd8FJDYtKTxNjkCCBf4Ni3y0dwWSrChm51wXI/FhjHaRXix5rKygtYwGr4C1QUitPdKUJ7xemILbcJw7JsDnBktqU20DfP9VfoaCxuoDCPJvc1hF1QF+wBNy6uKNYK6qA4mBFVRXawVlKHkPTfUbKJo65NuFJ1W0sNb1EjPgOQEUcakGbJIApRPQpoZ+1iaoQKqjCln2IJqYdpgrZGArEGaGke5pPzPZE/Juq0bjbtU9KPpc6MMTTGjPeyCfQV8AK4c2lwJRjQ3AAAAAElFTkSuQmCC);}
.expand {background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABwAAAAcCAYAAAByDd+UAAABD0lEQVRIS+3Wyw2CQBAG4F1Q8KadSAnYgR0YL164SCWYKDHxonZgB1ICdiI3QR6yCgSVXXaAkGDkwgXyZf6dYcCo5Qu37KFugIaxH5FkdH1+hSYErpBgPck9E8j35AkUBYE5TEkqs6EoN1iApWmCUC6QgYHRUpCCOYk0zDUNV6VMkIYJSFAJFKLQim8glAqyME1b2AQ0zZ0CRQtBHiyNEop+gRCsCvoGVsGgaAbWwSDoE2wC40VxkxgPiteb7QFhPMsNsEPmLG196DZgolF0fFXYd614M47jhxvBCtEIXfy7rGZnKEq3k4jEZd3KPhMhcxqgYBV4gylZZaXf0qqR0t77g00n2pG/tjpl/37TPACe/d8VUJ3+EgAAAABJRU5ErkJggg==);}
.elements {background-color: #ccd9ff;
overflow: hidden;}
<div class="panel">
<div id="header" class="collapse"><h2>Features</h2></div>
<div class="elements">
text<br>text<br>text
</div>
</div>

Edit your declaration block of h2 as shown below. This will solve your problem.
h2 {
display: inline-block;
margin: 0px;
padding: 0px 0px 0px 0px;
color: #ffffff;
text-align: center;
text-transform: uppercase;
pointer-events: none; // this line solves your problem.
}
CSS property pointer-events let you control under what circumstances an element can become the target of mouse events. when you set it to none, the element will never be the target of mouse events. So, the click event passed on to its descendant elements (here the box).