W3Schools Tryit Editor

<!DOCTYPE html>
<html>
<title>W3.CSS</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://www.w3schools.com/w3css/5/w3.css">
<style>
.mySlides {display:none}
</style>
<body>

<div class="w3-container">
  <h2>Slideshow Indicators</h2>
  <p>An example of using buttons to indicate how many slides there are in the slideshow, and which slide the user is currently viewing.</p>
</div>

function plusDivs(n) {
  showDivs(slideIndex += n);
}

function currentDiv(n) {
  showDivs(slideIndex = n);
}

</body>
</html>

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<!DOCTYPE html><html><title>W3.CSS</title><meta name="viewport" content="width=device-width, initial-scale=1"><link rel="stylesheet" href="https://www.w3schools.com/w3css/5/w3.css"><style>.mySlides {display:none}</style><body>​<div class="w3-container">  <h2>Slideshow Indicators</h2>  <p>An example of using buttons to indicate how many slides there are in the slideshow, and which slide the user is currently viewing.</p></div>​<div class="w3-content" style="max-width:800px">  <img class="mySlides" src="img_nature_wide.jpg" style="width:100%">  <img class="mySlides" src="img_snow_wide.jpg" style="width:100%">  <img class="mySlides" src="img_mountains_wide.jpg" style="width:100%"></div>​<div class="w3-center">  <div class="w3-section">    <button class="w3-button w3-light-grey" onclick="plusDivs(-1)">❮ Prev</button>    <button class="w3-button w3-light-grey" onclick="plusDivs(1)">Next ❯</button>  </div>  <button class="w3-button demo" onclick="currentDiv(1)">1</button>   <button class="w3-button demo" onclick="currentDiv(2)">2</button>   <button class="w3-button demo" onclick="currentDiv(3)">3</button> </div>​<script>var slideIndex = 1;showDivs(slideIndex);​function plusDivs(n) {  showDivs(slideIndex += n);}​function currentDiv(n) {  showDivs(slideIndex = n);}​function showDivs(n) {