how to create a slideshow in html

var slideIndex = 0;
showSlides();

function showSlides() {
  var i;

    var slides = document.getElementsByClassName("mySlides");
  
for (i = 0; i < slides.length; i++) {
    
slides[i].style.display = "none"; 
  }
  slideIndex++;

    if (slideIndex > slides.length) {slideIndex 
= 1} 
  slides[slideIndex-1].style.display = "block";

  setTimeout(showSlides, 2000); // Change image every 2 
seconds
} 

var slideIndex = 1;
showSlides(slideIndex);

// Next/previous controls
function plusSlides(n) 
{
  showSlides(slideIndex += n);
}

// Thumbnail image controls
function currentSlide(n) {
  
showSlides(slideIndex = n);
}

function showSlides(n) {
  
var i;
  var slides = document.getElementsByClassName("mySlides");
  
var dots = document.getElementsByClassName("dot");
  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";
}