We Keep Coding

Why does my image slider not automatically start?

I hope to get some help here. I think the solution can be very easy but I can't find the problem.
I created an image slider with changing buttons on click. I have the code from the internet and it works fine. The problem is that the carousel doesn't start automatically on the website starter page. The slideshow loop only starts if I click on the first picture.
This is how my .js code looks like. Regards :)
/*SLIDESHOW*/
var slideIndex = 0;
showSlide(slideIndex);
function plusSlides(n){
showSlide(slideIndex += n);
}
function currentSlide(n) {
showSlide(slideIndex = n);
}
function showSlide(n){
var i;
var slides = document.getElementsByClassName("myslides fade");
var dots = document.getElementsByClassName("dots");
if (n > slides.length) { slideIndex = 3};
if (n < 3) { slideIndex = slides.length};
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(showSlide, 3000);
}

Add your code inside a document.ready function and try,
$( document ).ready(function() {
//Your Code
});

Javascript Slideshow not working when using LocalStorage

I have a slideshow in JS and html which works fine until I use a variable stored in localStorage to define which slide to start from when the page refresh/reload.
What works:
- after the page has reloaded, the slideshow starts from the desired slide;
- after the page has reloaded and after the first command forward, the slideshow begins to work correctly.
What does not work:
- after the page has reloaded, moving the slideshow forward for the first time always makes the slideshow begins from the first slide;
- after the page has reloaded, moving the slideshow backward for the first time always makes the variable in the local storage undefined and the slides disappear.
I think the issue is with the showSlides(), but I cannot understand what it is.
Here is my code so far:
// Set local storage
var slideIx = localStorage.getItem('slideIndex');
if (slideIx === null) {
slideIx = 1;
}
var slideIndex = slideIx;
showSlides(slideIndex);
// Next/previous controls
function plusSlides(n) {
showSlides(slideIndex += n);
localStorage.setItem('slideIndex', slideIndex);
console.log(localStorage.getItem('slideIndex'));
}
// Thumbnail image controls
function currentSlides(n) {
showSlides(slideIndex = n);
localStorage.setItem('slideIndex', slideIndex);
console.log(localStorage.getItem('slideIndex'));
}
// Show slides
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";
}
// Arrows control
document.onkeydown = function(e) {
e = e || window.event;
if (e.keyCode == '37') {
e.preventDefault();
plusSlides(-1); //left <- show Prev image
} else if (e.keyCode == '39') {
e.preventDefault();
plusSlides(1); // right -> show next image
}
};
Thank you very much for any hint you might have(!).

I think the issue is that you need to convert string to number before you operate with it. The value retrieved from localStorage is always of a String type, while you expect number in your code. Try this:
var slideIx = Number(localStorage.getItem('slideIndex') || 1);
(then next check for null is not needed).

I succeeded the slideShow to show the last picture after refreshing the page by the next code (you can see it here https://jsfiddle.net/mu9otwcy/1/):
var myIndex;
if(localStorage.getItem('slideIx') === null){
myIndex = 0;
}
else{
myIndex = localStorage.getItem('slideIx') -1;
}
console.log(myIndex);
carousel();
function carousel() {
var i;
var x = document.getElementsByClassName("mySlides");
for (i = 0; i < x.length; i++) {
x[i].style.display = "none";
}
myIndex++;
console.log(myIndex);
if (myIndex > x.length) {
myIndex = 1;
}
x[myIndex-1].style.display = "block";
var slideIx = localStorage.setItem('slideIx',myIndex);
setTimeout(carousel, 3000);
}

How can I clear setInterval when a specific button is pressed?

I'm having a hard time coming up with a solution on how to clear setInterval when clicking on a specific button(with class "next"). My code is listed bellow, and I'm just starting to learn js and jquery so it's probably in a bad shape.
<script>
var slideIndex = 1;
showSlides(slideIndex);
function plusSlides(n) {
showSlides(slideIndex += n);
}
function showSlides(n) {
var i;
var slides = document.getElementsByClassName("mySlides");
if (n > slides.length) {slideIndex = 1}
if (n < 1) {slideIndex = slides.length}
for (i = 0; i < slides.length; i++) {
slides[i].style.display = "none";
}
slides[slideIndex-1].style.display = "block";
}
$(document).ready(function(){
function playslider(){
$('.next').trigger('click');
var x = setTimeout(function(){playslider()}, 5000);
}
playslider(); <!--To loop-->
});
</script>
Also if you wouldn't mind helping how can I make the first click to occur 5 seconds after the page is loaded.
Edit: To elaborate more, so you have bigger understanding of what I'm doing and with what I need help.
I am creating a simple automatic picture Slideshow, that has a Next and Previous button. I want to cancel the setInterval(missused with setTimout), when pressing on either Next or Previous button. And I'm having a hard time figuring out where to put the code and how it should look like to clear setInterval time, while simultaneously going to the next picture.

You mix jQuery and DOM in an unhealthy manner var slides = $(".mySlides");
You are looking for clearInterval if you use setInterval and clearTimeout if you use setTimeout
To delay execution use the page load:
var tId ;
function playslider(){
$('.next').trigger('click');
}
$(function() {
tId = setInterval(playslider,5000); // can be stopped with clearInterval(tId);
});

You are actually using setTimeout, not setInterval.
You can cancel timeout using clearTimeout(id)
You can also use setInterval instead:
var slideIndex = 1;
showSlides(slideIndex);
function plusSlides(n) {
showSlides(slideIndex += n);
}
function showSlides(n) {
var i;
var slides = document.getElementsByClassName("mySlides");
if (n > slides.length) {slideIndex = 1}
if (n < 1) {slideIndex = slides.length}
for (i = 0; i < slides.length; i++) {
slides[i].style.display = "none";
}
slides[slideIndex-1].style.display = "block";
}
$(document).ready(function(){
var intervalId = null;
function enablePlayback(){
if(intervalId == null) {
setInterval(function() {
$('.next').trigger('click'); // you should implement this differently, as this is bad practice.
}, 5000);
}
}
function disablePlayback() {
if(intervalId != null) {
clearInterval(intervalId);
intervalId = null;
}
}
enablePlayback(); <!--To loop-->
$('#ButtonToDisable').click(function() { disablePlayback(); });
$('#ButtonToEnable').click(function() { enablePlayback(); });
});

pause / play SlideShow (setInterval) in Javascript

to start things of I want to mention that I am very new at this and probably very bad and I have tried for weeks now, searched answers and so on and just couldn't implement something proper in my code. I want to simply pause / resume a slide animation. I managed to make most of it work, but the problem is the setInterval. mine is set to 10s. I have a fading-in-out animation that lasts also 10 secs. If i pause lets say after 5 secs and then resume, the animation will have 10 extra seconds adding up to 15, after which it will change the slide abruptly and I want a smooth transition.
What I could think of is to save the elapsed time from the interval at the moment of pausing and then subtract that value from the total time of the interval and set it for the remaining part. Problem is i don't know how to put that into code. :/
var slideIndex = 1;
var myIndex = 0;
var myVar;
var playing = true;
var pauseButton = document.getElementById("pause");
var y = document.getElementsByClassName("mySlides");
var k;
var div = document.getElementsByClassName("stuff");
var globaltime = 10000;
var slideInterval = setInterval(carousel, globaltime);
var milisec;
function plusDivs(n) {
showDivs(slideIndex += n);
}
function currentDiv(n) {
showDivs(slideIndex = n);
}
function showDivs(n) {
var i;
var x = document.getElementsByClassName("mySlides");
var dots = document.getElementsByClassName("demo");
if (n > x.length) {slideIndex = 1}
if (n < 1) {slideIndex = x.length}
for (i = 0; i < x.length; i++) {
x[i].style.display = "none";
}
for (i = 0; i < dots.length; i++) {
dots[i].className = dots[i].className.replace(" white", "");
}
x[slideIndex-1].style.display = "block";
dots[slideIndex-1].className += " white";
}
function carousel() {
var i;
var x = document.getElementsByClassName("mySlides");
var dots = document.getElementsByClassName("demo");
for (i = 0; i < x.length; i++) {
x[i].style.display = "none";
}
myIndex++;
if (myIndex > x.length) {myIndex = 1}
for (i = 0; i < dots.length; i++) {
dots[i].className = dots[i].className.replace(" white", "");
}
x[myIndex-1].style.display = "block";
dots[myIndex-1].className += " white";
}
function pauseSlideshow(){
pauseButton.innerHTML = '►';
playing = false;
t = slideInterval;
clearInterval(slideInterval);
for (k = 0; k < div.length; k++) {
div[k].className = div[k].className.replace(" running", " paused");
}
}
function playSlideshow(){
pauseButton.innerHTML = '❙❙';
playing = true;
slideInterval = setInterval(carousel, globaltime);
for (k = 0; k < div.length; k++) {
div[k].className = div[k].className.replace(" paused", " running");
}
}
function stop(){
if(playing){
pauseSlideshow();
}
else {
playSlideshow();
}
}
carousel();
timer();
showDivs(slideIndex);
Thank you very much in advance for your time, patience and understanding.

Stop Slide Show on mouse over in Javascript

I am using following java-script for a slide show, now I like to pause the loop on mouse-over event on the element "dot", my expertise in java is zero, please help.
<script>
var slideIndex = 0;
showSlides();
function showSlides() {
var i;
var slides = document.getElementsByClassName("mySlides");
var 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, 5000); // Change text every 5 seconds
}
</script>

A few things. Firstly, I would suggest using setInterval() instead. This allows you to easily stop the timer outside of the function. The syntax is identical to setTimeout(). setInterval() is very similar to setTimeout(), except it will continue to execute the function (the first parameter) until you call clearInterval().
Note that setInterval() (and setTimeout()) returns a value, which can be used for clearInterval() and clearTimeout(), respectively.
Changing your code to utilize setInterval should be fairly straightforward. Given what you have posted above, it might look something like this:
<script>
var slideIndex = 0;
showSlides();
function showSlides() {
var i;
var slides = document.getElementsByClassName("mySlides");
var 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";
}
var interval = setInterval(showSlides, 5000); // Change text every 5 seconds
Note that I save interval as a variable that can be used later to stop the timer.
Once you have made this change, the solution to your main question becomes much easier. You can set up event handlers by adding the following:
function pauseSlides(event)
{
clearInterval(interval); // Clear the interval we set earlier
}
function resumeSlides(event)
{
interval = setInterval(showSlides, 5000);
}
// Set up event listeners for the dots
var dots = document.getElementsByClassName("dot");
for (i = 0; i < dots.length; i++) {
dots[i].onmouseover = pauseSlides;
dots[i].onmouseout = resumeSlides;
}
The entirety of your code, given the above, may now look something like this:
<script>
var slideIndex = 0;
showSlides();
function showSlides() {
var i;
var slides = document.getElementsByClassName("mySlides");
var 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";
}
var interval = setInterval(showSlides, 5000); // Change text every 5 seconds
// Set up event listeners for the dots
var dots = document.getElementsByClassName("dot");
for (i = 0; i < dots.length; i++) {
dots[i].onmouseover = pauseSlides;
dots[i].onmouseout = resumeSlides;
}
function pauseSlides()
{
clearInterval(interval); // Clear the interval we set earlier
}
function resumeSlides()
{
interval = setInterval(showSlides, 5000);
}
</script>
Additionally, for reference:
setInterval() reference: https://www.w3schools.com/jsref/met_win_setinterval.asp
Events in JavaScript: https://www.w3schools.com/jsref/dom_obj_event.asp

Wonderful Aaron, much appreciated response. I just checked the code and its working perfectly.
Can we modify this code further and on-mouse over event we can go to specific slide? i mean by using the same "dot" element? The dots are representing different slides, so I want if a user trigger mouse over event on any dot, the slide display benith that specific dot element.