Simple Responsive Slideshow With CSS JS (Free Download)

Welcome to a tutorial on how to create a simple responsive slideshow with pure CSS and vanilla Javascript. Yes, there are a lot of crazy slideshow plugins on the Internet. But some of them require the use of third-party libraries, which adds to the undesired loading bloat – So here it is, a simple and lightweight slideshow that you can use. Read on!

ⓘ I have included a zip file with all the source code at the start of this tutorial, so you don’t have to copy-paste everything… Or if you just want to dive straight in.

 

TABLE OF CONTENTS

Download & Demo	How It Works	Auto Load Slides
The End

 

 

 

QUICK NOTES

If you spot a bug, feel free to comment below. I try to answer short questions too, but it is one person versus the entire world… If you need answers urgently, please check out my list of websites to get help with programming.

 

SOURCE CODE DOWNLOAD

Click here to download the source code, I have released it under the MIT license, so feel free to build on top of it or use it in your own project.

 

HOW TO USE & DEMO

<!-- (A) LOAD LIBRARY -->
<link rel="stylesheet" href="slides.css"/>
<script defer src="slides.js"></script>

<!-- (B) CREATE HTML DIV -->
<div id="slidedemo"></div>

<!-- (C) ATTACH SLIDESHOW -->
<script>
window.addEventListener("DOMContentLoaded", () => {
  sslide.init({
    target: "slidedemo",
    images: [
      {src: "cat.jpg", cap: "An evil cate."},
      {src: "dove.jpg", cap: "A birb."},
      {src: "fox.jpg", cap: "Not a doge."}
    ],
    // (OPTIONAL) 3 SEC PER SLIDE, REMOVE TO MANUAL SCROLL
    auto: 3000
  });
});
</script>

1. Captain Obvious, load both slides.css and slides.js.
2. Define a <div> to attach the slideshow to.
3. Lastly, use sslide.init() to attach the slideshow. There are only 3 options here:
   • target ID of the <div> element that you want to attach the slideshow to.
   • images Array of images you want to show. Remember to provide both the source URL and caption.
   • auto In milliseconds, optional. Automatically rotate between the slides.

 

 

 

PART 1) PRELOAD IMAGES

/* (A) INITIALIZE - PRELOAD IMAGES */
instances : [],
init : (opt) => {
  // (A1) REGISTER SLIDESHOW INSTANCE
  const id = sslide.instances.length;
  sslide.instances.push(opt);
 
  // (A2) PRELOAD IMAGES
  let loaded = 0, ready = () => {
    loaded++;
    if (loaded == opt.images.length) { sslide.attach(id); }
  };
  for (let i of opt.images) {
    let img = new Image();
    img.src = i.src;
    img.onload = ready;
  }
}

The sslide.init() function is what we call to initialize the slideshow.

• (A1) Very simply, we push a new instance into the sslide.instances array. Yes, we need to support multiple slideshows on a single page, and this is used to track which is which.
• (A2) Proceed with the next step only when all the images are preloaded.

 

 

PART 2) ATTACH HTML INTERFACE

/* (B) INITIALIZE - ATTACH HTML CONTROLS */
attach : (id) => {
  // (B1) GET HTML CONTAINER
  let inst = sslide.instances[id],
      sSlide = document.getElementById(inst.target);
 
  // (B2) SLIDESHOW HTML INTERFACE
  let sImg = document.createElement("img"),
      sCaption = document.createElement("div"),
      sLeft = document.createElement("div"),
      sRight = document.createElement("div");
  sSlide.className = "sSlide";
  sImg.className = "sImg";
  sCaption.className = "sCaption";
  sLeft.className = "sLeft";
  sRight.className = "sRight";
  sLeft.innerHTML = "<";
  sRight.innerHTML = ">";
  sLeft.addEventListener("click", () => { sslide.nav(id, 0); });
  sRight.addEventListener("click", () => { sslide.nav(id, 1); });
  sSlide.appendChild(sImg);
  sSlide.appendChild(sCaption);
  sSlide.appendChild(sLeft);
  sSlide.appendChild(sRight);
 
  // (B3) READY!
  inst.current = -1;
  inst.sImg = sImg;
  inst.sCaption = sCaption;
  sslide.nav(id, 1);
}

Ok, this looks crazy. But all it does is essentially generate the following HTML:

<div id="slidedemo" class="sSlide">
  <div class="sImg"></div>
  <div class="sCaption"></div>
  <div class="sLeft" onclick="sslide.nav(ID, 0)">&lt;</div>
  <div class="sRight" onclick="sslide.nav(ID, 1)">&gt;</div>
</div>

 

 

PART 3) DRAW CURRENT SLIDE

/* (C) NAVIGATION */
nav : (id, direction) => {
  // (C1) CALCULATE NEXT SLIDE
  let inst = sslide.instances[id],
      slides = inst.images;
  if (direction) { inst.current++; }
  else { inst.current--; }
  if (inst.current < 0) { inst.current = slides.length - 1; }
  if (inst.current >= slides.length) { inst.current = 0; }
 
  // (C2) DRAW SLIDE
  inst.sImg.src = slides[inst.current].src;
  inst.sCaption.innerHTML = slides[inst.current].cap;
 
  // (C3) AUTO SCROLL MODE
  if (inst.auto) {
    if (inst.timer) { clearInterval(inst.timer); }
    inst.timer = setInterval(() => { sslide.nav(id, 1); }, inst.auto);
  }
}

sslide.nav() is fired whenever the user clicks on left/right. Should be pretty self-explanatory –

• We update the current slide – inst.current.
• Get the image source and caption – inst.images[CURRENT].
• Update the HTML.
• Reset the timer if necessary for auto-scroll.

That’s all!

 

PART 4) THE CSS

/* (A) SHARED */
.sImg, .sCaption { width: 100%; }
.sSlide, .sLeft, .sRight { display: flex; }
 
/* (B) CONTAINER */
.sSlide {
  flex-wrap: wrap;
  position: relative;
  max-width: 640px;
}
 
/* (C) IMAGE */
.sImg {
  height: 350px;
  object-fit: cover; /* fill, contain, scale-down */
}

/* (D) CAPTION */
.sCaption {
  padding: 10px;
  color: #fff;
  background: #000;
}
 
/* (E) CONTROLS */
/* (E1) LEFT/RIGHT BUTTONS */
.sLeft, .sRight {
  align-items: center;
  position: absolute;
  top: 0;
  z-index: 9;
  height: 100%;
  padding: 0 20px;
  font-size: 2em;
  color: #fff;
  background: rgba(0, 0, 0, 0.5);
  cursor: pointer;
}
.sTop .sLeft { left: 0; }
.sTop .sRight { right: 0; }
 
/* (E2) SHOW ONLY ON HOVER */
.sLeft, .sRight {
  visibility: hidden;
  opacity: 0;
  transition: opacity 0.3s;
}
.sSlide:hover .sLeft, .sSlide:hover .sRight {
  visibility: visible;
  opacity: 1;
}

Yep… Don’t think I want to dive too deep into the CSS – These are practically the cosmetics of the slideshow. Feel free to change the colors and layout to fit your own theme.

 

 

 

USING PHP TO AUTOLOAD ALL SLIDES

Lazy to change the HTML every time? Use a server-side script to help you extract all the image files automatically. Here’s a quick example in PHP.

<script>
window.addEventListener("DOMContentLoaded", () => {
  sslide.init({
    target: "slidedemo",
    images: [<?php
      $dir = "gallery/";
      $images = glob($dir . "*.{jpg,jpeg,gif,png,bmp,webp}", GLOB_BRACE);
      $all = count($images);
      $last = $all - 1;
      for ($i=0; $i<$all; $i++) {
        printf('{src:"%s%s", cap:"%s"}%s',
          $dir, basename($images[$i]), basename($images[$i]),
          $i==$last ? "" : ","
        );
      }
    ?>]
});
</script>

 

COMPATIBILITY CHECKS

• Arrow Functions – CanIUse
• CSS Flexbox – CanIUse

Should work across all major browsers… Less the “ancient ones”.