Learn how to create a Comparison Slider with CSS and JavaScript.

Demo:
Before & After:
What do you need to do?
- Add HTML
- Add CSS
- Add JavaScript
Step1.
Add HTML
Add images that you want to compare:
<div class="img-comp-container">
<div class="img-comp-img">
<img src="https://lenadesign.org/wp-content/uploads/2021/04/make-up-1.jpg" width="640" height="480">
</div>
<div class="img-comp-img img-comp-overlay">
<img src="https://lenadesign.org/wp-content/uploads/2021/04/no-make-up-1.jpg" width="640" height="480">
</div>
</div>
Step2.
Add CSS
Set the colour and the position of the background and elements:
body {
background-color: #eae2b7;
display: flex;
align-items: center;
justify-content: center;
height: 100vh;
}
.img-comp-container {
left:-50px;
position: relative;
height: 480px;
width: 640px;
border: 10px solid #e63946;
}
Set the position of the images:
.img-comp-img {
position: absolute;
width: auto;
height: auto;
overflow:hidden;
}
.img-comp-img img {
display:block;
vertical-align:middle;
}
Style the slider:
.img-comp-slider {
position: absolute;
cursor: ew-resize;
width: 3px;
height: 480px;
background-color: white;
color: white;
}
.img-comp-slider {
position: absolute;
cursor: ew-resize;
width: 3px;
height: 480px;
background-color: white;
color: white;
}
.img-comp-slider:before {
content:"";
position: absolute;
content: url("https://lenadesign.org/wp-content/uploads/2021/04/dot-2.png");
top:220px;
left:-34px;
}
.img-comp-slider:hover {
box-shadow: 0 0 10px rgba(0,0,0,0.3);
}
Step3.
Add JavaScript
function initComparisons() {
var x, i;
x = document.getElementsByClassName("img-comp-overlay");
for (i = 0; i < x.length; i++) {
compareImages(x[i]);
}
function compareImages(img) {
var slider, img, clicked = 0, w, h;
w = img.offsetWidth;
h = img.offsetHeight;
img.style.width = (w / 2) + "px";
/*slider:*/
slider = document.createElement("DIV");
slider.style.zIndex = "10";
slider.setAttribute("class", "img-comp-slider");
img.parentElement.insertBefore(slider, img);
slider.style.left = (w / 2) - (slider.offsetWidth / 2) + "px";
slider.addEventListener("mousedown", slideReady);
window.addEventListener("mouseup", slideFinish);
slider.addEventListener("touchstart", slideReady);
window.addEventListener("touchend", slideFinish);
function slideReady(e) {
e.preventDefault();
clicked = 1;
window.addEventListener("mousemove", slideMove);
window.addEventListener("touchmove", slideMove);
}
function slideFinish() {
clicked = 0;
}
function slideMove(e) {
var pos;
if (clicked == 0) return false;
pos = getCursorPos(e)
if (pos < 0) pos = 0;
if (pos > w) pos = w;
slide(pos);
}
function getCursorPos(e) {
var a, x = 0;
e = e || window.event;
a = img.getBoundingClientRect();
x = e.pageX - a.left;
x = x - window.pageXOffset;
return x;
}
function slide(x) {
img.style.width = x + "px";
slider.style.left = img.offsetWidth - (slider.offsetWidth / 2) + "px";
}
}
}
initComparisons();
Enjoy coding!
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