Automatic slideshow with button

css, html, javascript, slideshow

Solution

You did not declare the functions to make slider move on button click ,

I added some instruction that make slider work for both dots and left right buttons , see bellow snippet , kindly run the snippet in full screen .

var slideIndex = 0;
showSlides();
var slides,dots;

function showSlides() {
    var i;
    slides = document.getElementsByClassName("mySlides");
    dots = document.getElementsByClassName("dot");
    for (i = 0; i < slides.length; i++) {
       slides[i].style.display = "none";  
    }
    slideIndex++;
    if (slideIndex> slides.length) {slideIndex = 1}    
    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";
    setTimeout(showSlides, 8000); // Change image every 8 seconds
}

function plusSlides(position) {
    slideIndex +=position;
    if (slideIndex> slides.length) {slideIndex = 1}
    else if(slideIndex<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";
}

function currentSlide(index) {
    if (index> slides.length) {index = 1}
    else if(index<1){index = 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[index-1].style.display = "block";  
    dots[index-1].className += " active";
}

#slide{
 width:96%;
 }
 
* {
 box-sizing: border-box
}

.mySlides {
 display: none
}

.slideshow-container {
 width: 1200px;
 position: relative;
 margin: -10px;

}
/* Next & previous buttons */
.prev, .next {
 cursor: pointer;
 position: absolute;
 top: 50%;
 width: auto;
 padding: 16px;
 margin-top: -22px;
 color: white;
 font-weight: bold;
 font-size: 18px;
 transition: 0.6s ease;
 border-radius: 0 3px 3px 0;
}
/* 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);
}
/* Caption text */
.text {
 color: #f2f2f2;
 font-size: 15px;
 padding: 8px 12px;
 position: absolute;
 bottom: 8px;
 width: 100%;
 text-align: center;
}

/* The dots/bullets/indicators */
.dot {
 cursor: pointer;
 height: 13px;
 width: 13px;
 margin: 0 2px;
 background-color: #bbb;
 border-radius: 50%;
 display: inline-block;
 transition: background-color 0.6s ease;
}
.active, .dot:hover {
 background-color: #717171;
}
/* Fading animation */
.fade {
 -webkit-animation-name: fade;
 -webkit-animation-duration: 2s;
 animation-name: fade;
 animation-duration: 2s;
}
@-webkit-keyframes fade {
  from {opacity: .4} 
  to {opacity: 1}
}

@keyframes fade {
  from {opacity: .4} 
  to {opacity: 1}
}

/* On smaller screens, decrease text size */
@media only screen and (max-width: 300px) {
  .text {font-size: 11px}
}

<div id="slide">
  <div class="slideshow-container">
    <div class="mySlides fade"> <img src="https://www.w3schools.com/howto/img_nature_wide.jpg" style="width:100%"> </div>
    <div class="mySlides fade"> <img src="https://www.w3schools.com/howto/img_snow_wide.jpg" style="width:100%"> </div>
    <div class="mySlides fade"> <img src="https://www.w3schools.com/howto/img_lights_wide.jpg" style="width:100%"> </div>
    <div class="mySlides fade"> <img src="https://www.w3schools.com/howto/img_mountains_wide.jpg" style="width:100%"> </div>
    <a class="prev" onclick="plusSlides(-1)">&#10094;</a> <a class="next" onclick="plusSlides(1)">&#10095;</a> </div>
  <br>
  <div style="text-align:center"> 
  <span class="dot" onclick="currentSlide(1)"></span> 
  <span class="dot" onclick="currentSlide(2)"></span> 
  <span class="dot" onclick="currentSlide(3)"></span>
  <span class="dot" onclick="currentSlide(4)"></span>
   </div>

Problem

Original source