Have a slideshow gallery with preview images change a CSS attribute automatically-CodePudding

(Sorry for the confusing title)

So, I wanted to make a slideshow gallery, which I found here: https://www.w3schools.com/howto/howto_js_slideshow_gallery.asp

As you can see, there are previews of the images in a small bar below the main image that's being shown. Each preview image has width: 16.66%;, since 6*16.66 ~ 100%.

The thing is, in my application, I have to have several galleries(let's say, for example, 5 galleries), with different amount of images in them. I could make 5 different galleries, each with a "unique" name for the container of the preview image, and be done with it, but I'm looking for a more "automated" way, which will be more sustainable if I want to create another gallery down the line. And all that because of the line that controls the width of the preview image.

For example, let's say I want to make one gallery has 11 pictures, in addition to the one with the 6 images that's present in the site. Following the same logic, each preview image would have to have width: 9.09%;. Can I somehow "tell" CSS that I want the width to be 9.09% in one case, and 16.66% in the other?

Thank you in advance and sorry for the confusing question.

CodePudding user response：

Remove float:left for the column and add display:flex for the row parent it will automatically allocate width for the children.

<!DOCTYPE html>
<html>
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
body {
  font-family: Arial;
  margin: 0;
}

* {
  box-sizing: border-box;
}

img {
  vertical-align: middle;
}

/* Position the image container (needed to position the left and right arrows) */
.container {
  position: relative;
}

/* Hide the images by default */
.mySlides {
  display: none;
}

/* Add a pointer when hovering over the thumbnail images */
.cursor {
  cursor: pointer;
}

/* Next & previous buttons */
.prev,
.next {
  cursor: pointer;
  position: absolute;
  top: 40%;
  width: auto;
  padding: 16px;
  margin-top: -50px;
  color: white;
  font-weight: bold;
  font-size: 20px;
  border-radius: 0 3px 3px 0;
  user-select: none;
  -webkit-user-select: none;
}

/* Position the "next button" to the right */
.next {
  right: 0;
  border-radius: 3px 0 0 3px;
}

/* On hover, add a black background color with a little bit see-through */
.prev:hover,
.next:hover {
  background-color: rgba(0, 0, 0, 0.8);
}

/* Number text (1/3 etc) */
.numbertext {
  color: #f2f2f2;
  font-size: 12px;
  padding: 8px 12px;
  position: absolute;
  top: 0;
}

/* Container for image text */
.caption-container {
  text-align: center;
  background-color: #222;
  padding: 2px 16px;
  color: white;
}

.row:after {
  content: "";
  display: table;
  clear: both;
}

/* 11 columns side by side */
.row {
display: flex;}

/* Add a transparency effect for thumnbail images */
.demo {
  opacity: 0.6;
}

.active,
.demo:hover {
  opacity: 1;
}
</style>
<body>

<h2 style="text-align:center">Slideshow Gallery</h2>

<div class="container">
  <div class="mySlides">
    <div class="numbertext">1 / 6</div>
    <img src="https://www.w3schools.com/howto/img_woods_wide.jpg" style="width:100%">
  </div>

  <div class="mySlides">
    <div class="numbertext">2 / 6</div>
    <img src="https://www.w3schools.com/howto/img_5terre_wide.jpg" style="width:100%">
  </div>

  <div class="mySlides">
    <div class="numbertext">3 / 6</div>
    <img src="https://www.w3schools.com/howto/img_mountains_wide.jpg" style="width:100%">
  </div>
    
  <div class="mySlides">
    <div class="numbertext">4 / 6</div>
    <img src="https://www.w3schools.com/howto/img_lights_wide.jpg" style="width:100%">
  </div>

  <div class="mySlides">
    <div class="numbertext">5 / 6</div>
    <img src="https://www.w3schools.com/howto/img_nature_wide.jpg" style="width:100%">
  </div>
    
  <div class="mySlides">
    <div class="numbertext">6 / 6</div>
    <img src="https://www.w3schools.com/howto/img_snow_wide.jpg" style="width:100%">
  </div>
    
  <a class="prev" onclick="plusSlides(-1)">❮</a>
  <a class="next" onclick="plusSlides(1)">❯</a>

  <div class="caption-container">
    <p id="caption"></p>
  </div>

  <div class="row">
    <div class="column">
      <img class="demo cursor" src="https://www.w3schools.com/howto/img_woods.jpg" style="width:100%" onclick="currentSlide(1)" alt="The Woods">
    </div>
    <div class="column">
      <img class="demo cursor" src="https://www.w3schools.com/howto/img_5terre.jpg" style="width:100%" onclick="currentSlide(2)" alt="Cinque Terre">
    </div>
    <div class="column">
      <img class="demo cursor" src="https://www.w3schools.com/howto/img_mountains.jpg" style="width:100%" onclick="currentSlide(3)" alt="Mountains and fjords">
    </div>
    <div class="column">
      <img class="demo cursor" src="https://www.w3schools.com/howto/img_lights.jpg" style="width:100%" onclick="currentSlide(4)" alt="Northern Lights">
    </div>
    <div class="column">
      <img class="demo cursor" src="https://www.w3schools.com/howto/img_nature.jpg" style="width:100%" onclick="currentSlide(5)" alt="Nature and sunrise">
    </div>    
    <div class="column">
      <img class="demo cursor" src="https://www.w3schools.com/howto/img_snow.jpg" style="width:100%" onclick="currentSlide(6)" alt="Snowy Mountains">
    </div>
    <div class="column">
      <img class="demo cursor" src="https://www.w3schools.com/howto/img_woods.jpg" style="width:100%" onclick="currentSlide(1)" alt="The Woods">
    </div>
    <div class="column">
      <img class="demo cursor" src="https://www.w3schools.com/howto/img_5terre.jpg" style="width:100%" onclick="currentSlide(2)" alt="Cinque Terre">
    </div>
    <div class="column">
      <img class="demo cursor" src="https://www.w3schools.com/howto/img_mountains.jpg" style="width:100%" onclick="currentSlide(3)" alt="Mountains and fjords">
    </div>
    <div class="column">
      <img class="demo cursor" src="https://www.w3schools.com/howto/img_lights.jpg" style="width:100%" onclick="currentSlide(4)" alt="Northern Lights">
    </div>
    <div class="column">
      <img class="demo cursor" src="https://www.w3schools.com/howto/img_nature.jpg" style="width:100%" onclick="currentSlide(5)" alt="Nature and sunrise">
    </div>
  </div>
</div>

<script>
var slideIndex = 1;
showSlides(slideIndex);

function plusSlides(n) {
  showSlides(slideIndex  = n);
}

function currentSlide(n) {
  showSlides(slideIndex = n);
}

function showSlides(n) {
  var i;
  var slides = document.getElementsByClassName("mySlides");
  var dots = document.getElementsByClassName("demo");
  var captionText = document.getElementById("caption");
  if (n > slides.length) {slideIndex = 1}
  if (n < 1) {slideIndex = slides.length}
  for (i = 0; i < slides.length; i  ) {
      slides[i].style.display = "none";
  }
  for (i = 0; i < dots.length; i  ) {
      dots[i].className = dots[i].className.replace(" active", "");
  }
  slides[slideIndex-1].style.display = "block";
  dots[slideIndex-1].className  = " active";
  captionText.innerHTML = dots[slideIndex-1].alt;
}
</script>
    
</body>
</html>

Same code here with 6 thumbs

<!DOCTYPE html>
<html>
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
body {
  font-family: Arial;
  margin: 0;
}

* {
  box-sizing: border-box;
}

img {
  vertical-align: middle;
}

/* Position the image container (needed to position the left and right arrows) */
.container {
  position: relative;
}

/* Hide the images by default */
.mySlides {
  display: none;
}

/* Add a pointer when hovering over the thumbnail images */
.cursor {
  cursor: pointer;
}

/* Next & previous buttons */
.prev,
.next {
  cursor: pointer;
  position: absolute;
  top: 40%;
  width: auto;
  padding: 16px;
  margin-top: -50px;
  color: white;
  font-weight: bold;
  font-size: 20px;
  border-radius: 0 3px 3px 0;
  user-select: none;
  -webkit-user-select: none;
}

/* Position the "next button" to the right */
.next {
  right: 0;
  border-radius: 3px 0 0 3px;
}

/* On hover, add a black background color with a little bit see-through */
.prev:hover,
.next:hover {
  background-color: rgba(0, 0, 0, 0.8);
}

/* Number text (1/3 etc) */
.numbertext {
  color: #f2f2f2;
  font-size: 12px;
  padding: 8px 12px;
  position: absolute;
  top: 0;
}

/* Container for image text */
.caption-container {
  text-align: center;
  background-color: #222;
  padding: 2px 16px;
  color: white;
}

.row:after {
  content: "";
  display: table;
  clear: both;
}

/* Six columns side by side */
.row {display: flex;}

/* Add a transparency effect for thumnbail images */
.demo {
  opacity: 0.6;
}

.active,
.demo:hover {
  opacity: 1;
}
</style>
<body>

<h2 style="text-align:center">Slideshow Gallery</h2>

<div class="container">
  <div class="mySlides">
    <div class="numbertext">1 / 6</div>
    <img src="img_woods_wide.jpg" style="width:100%">
  </div>

  <div class="mySlides">
    <div class="numbertext">2 / 6</div>
    <img src="img_5terre_wide.jpg" style="width:100%">
  </div>

  <div class="mySlides">
    <div class="numbertext">3 / 6</div>
    <img src="img_mountains_wide.jpg" style="width:100%">
  </div>
    
  <div class="mySlides">
    <div class="numbertext">4 / 6</div>
    <img src="img_lights_wide.jpg" style="width:100%">
  </div>

  <div class="mySlides">
    <div class="numbertext">5 / 6</div>
    <img src="img_nature_wide.jpg" style="width:100%">
  </div>
    
  <div class="mySlides">
    <div class="numbertext">6 / 6</div>
    <img src="img_snow_wide.jpg" style="width:100%">
  </div>
    
  <a class="prev" onclick="plusSlides(-1)">❮</a>
  <a class="next" onclick="plusSlides(1)">❯</a>

  <div class="caption-container">
    <p id="caption"></p>
  </div>

  <div class="row">
    <div class="column">
      <img class="demo cursor" src="img_woods.jpg" style="width:100%" onclick="currentSlide(1)" alt="The Woods">
    </div>
    <div class="column">
      <img class="demo cursor" src="img_5terre.jpg" style="width:100%" onclick="currentSlide(2)" alt="Cinque Terre">
    </div>
    <div class="column">
      <img class="demo cursor" src="img_mountains.jpg" style="width:100%" onclick="currentSlide(3)" alt="Mountains and fjords">
    </div>
    <div class="column">
      <img class="demo cursor" src="img_lights.jpg" style="width:100%" onclick="currentSlide(4)" alt="Northern Lights">
    </div>
    <div class="column">
      <img class="demo cursor" src="img_nature.jpg" style="width:100%" onclick="currentSlide(5)" alt="Nature and sunrise">
    </div>    
    <div class="column">
      <img class="demo cursor" src="img_snow.jpg" style="width:100%" onclick="currentSlide(6)" alt="Snowy Mountains">
    </div>
  </div>
</div>

<script>
var slideIndex = 1;
showSlides(slideIndex);

function plusSlides(n) {
  showSlides(slideIndex  = n);
}

function currentSlide(n) {
  showSlides(slideIndex = n);
}

function showSlides(n) {
  var i;
  var slides = document.getElementsByClassName("mySlides");
  var dots = document.getElementsByClassName("demo");
  var captionText = document.getElementById("caption");
  if (n > slides.length) {slideIndex = 1}
  if (n < 1) {slideIndex = slides.length}
  for (i = 0; i < slides.length; i  ) {
      slides[i].style.display = "none";
  }
  for (i = 0; i < dots.length; i  ) {
      dots[i].className = dots[i].className.replace(" active", "");
  }
  slides[slideIndex-1].style.display = "block";
  dots[slideIndex-1].className  = " active";
  captionText.innerHTML = dots[slideIndex-1].alt;
}
</script>
    
</body>
</html>

Flex reference: https://www.w3schools.com/cssref/css3_pr_flex.asp

Perhaps try a thumbnail carousel if you want a slider.