Develop Reference

Javascript image slideshow using a for loop

i'm trying to cycle through 3 images using a for loop in javascript. Here is my code:
<img name="slide" width="300" height="300">
var i=0;
var images = [];
images[0] = "images/1.jpg";
images[1] = "images/2.jpg";
images[2] = "images/3.jpg";
function changeImage () {
for(i=0; i < images.length; i++) {
document.slide.src = images[i];
}
}
window.onload = changeImage;
Currently, only image 3 is displayed. Anyone know what i'm doing wrong here?

Yes - this is because your for loop run finishes instantly so there's no time for slides 1 and 2 to be shown.
Give this a try:
var currentImage = 0,
images = [
"https://unsplash.it/200/300?image=100",
"https://unsplash.it/200/300?image=101",
"https://unsplash.it/200/300?image=102"
];
function initSlideshow() {
setImage(0);
setInterval(function(){
nextImage();
},1000);
}
function nextImage() {
if(images.length === currentImage + 1){
currentImage = 0;
} else {
currentImage++;
}
setImage(currentImage);
}
function setImage(image) {
document.querySelectorAll('.slide')[0].src = images[image];
}
window.onload = initSlideshow();
Example: https://jsfiddle.net/vvbdwazc/

Currently, only image 3 is displayed. Anyone know what i'm doing wrong
here?
it's all being displayed but the reason why you can only see the 3rd image is because you're not pausing for a certain time before displaying the next image hence it seems like it's not working.
use setInterval() method to show each image after a specified time.
Example:
var i=0;
var images = [];
images[0] = "images/1.jpg";
images[1] = "images/2.jpg";
images[2] = "images/3.jpg";
function changeImage () {
for(i=0; i < images.length; i++) {
document.slide.src = images[i];
}
}
var myVar = setInterval(function(){ changeImage() }, 1000);
You may later wish to prevent the setInterval() method from executing any longer in that case have a look at clearInterval().

window.onload = changeImage; tells me you want to change the image on page load event? In other words, the image changes only upon page load (or refresh).
Since state is not maintained by default (eg local storage or session storage or cookies) your best bet would be to use a random generator to choose randomly. See Generating random whole numbers in JavaScript in a specific range?

This is because the for works so fast it gets quickly to the third image. You could use instead some setInterval like this:
<img id="slide" width="300" height="300">
<script>
var images = [];
images[0] = "images/1.jpg";
images[1] = "images/2.jpg";
images[2] = "images/3.jpg";
var i = 0;
setInterval(function() {
var slide = document.querySelector("#slide"); //Select the img element by ID
slide.src = images[i++];
if(i > images.length - 1)
i = 0;
}, 1000); //Time in milliseconds
</script>
This will change constantly back to the first image when it reaches the last one.
Edit: Forgot to mention. setInterval works like a "repeater", it will work indefinitely until you clear it. To clear it you need to asign it to a variable and then use clearInterval passing the variable.
var interval = setInterval(function(){}, 1000) //example
clearInterval(interval);
Like so.

How do you restate setInterval after clearInterval has already been declared?

I realize there are more than a few answers on here about this but this particular instance has a very individual problem. I need to, on click, replay this png sequence after clearInterval has been used.
var myImage = document.getElementById("myImage");
var animationArray = ['assets/calvin_hobbes_dance00.png',
'assets/calvin_hobbes_dance01.png',
'assets/calvin_hobbes_dance02.png',
'assets/calvin_hobbes_dance03.png',
'assets/calvin_hobbes_dance04.png',
'assets/calvin_hobbes_dance05.png',
'assets/calvin_hobbes_dance06.png',
'assets/calvin_hobbes_dance07.png',
'assets/calvin_hobbes_dance08.png',
'assets/calvin_hobbes_dance09.png',
'assets/calvin_hobbes_dance10.png'];
var animationIndex = 0;
function changeImage () {
myImage.setAttribute("src", animationArray[animationIndex]);
animationIndex++;
if (animationIndex >= animationArray.length) {
animationIndex = 10;
clearInterval(intervalHandler);
}
}
var intervalHandler = setInterval(changeImage, 100);
A secondary question, this is merely a code sample. How might I wrap this so I can use it for elements that have animations attached that when upon focus play the animation?
Thank you.

Just add an onclick handler to your image. In the onclick handler, reset the animationIndex to 0, call clearInterval to clear the interval if it is running, and call the setInterval function again.
var myImage = document.getElementById("myImage");
var animationArray = ['assets/calvin_hobbes_dance00.png',
'assets/calvin_hobbes_dance01.png',
'assets/calvin_hobbes_dance02.png',
'assets/calvin_hobbes_dance03.png',
'assets/calvin_hobbes_dance04.png',
'assets/calvin_hobbes_dance05.png',
'assets/calvin_hobbes_dance06.png',
'assets/calvin_hobbes_dance07.png',
'assets/calvin_hobbes_dance08.png',
'assets/calvin_hobbes_dance09.png',
'assets/calvin_hobbes_dance10.png'];
var animationIndex = 0;
function changeImage () {
myImage.setAttribute("src", animationArray[animationIndex]);
animationIndex++;
if (animationIndex >= animationArray.length) {
animationIndex = 10;
clearInterval(intervalHandler);
}
}
myImage.onclick = function() {
animationIndex = 0;
clearInterval(intervalHandler);
intervalHandler = setInterval(changeImage, 100);
};
var intervalHandler = setInterval(changeImage, 100);
To answer your secondary question, you might want to consider another approach because this could get kind of messy and be hard to maintain in the future. Consider learning how to do animations using HTML canvas. Here is a tutorial I found showing how you could create multiple animations: http://www.williammalone.com/articles/create-html5-canvas-javascript-sprite-animation/
In fact, I would advise to change your implementation to use the canvas instead.

Javascript image slider setInterval()

I am making a simple image slider that runs through a directory containing images. The images is called "img_1", "img_2" and "img_3", so the point is to just iterate through them. The thing I don't get is how to implement a interval though. I want the images appear for 3 seconds, then change. The function "imgSlider" is on body load.
Edit: I am looking for simple solutions (in pure JS) as I am currently learning JS. Sorry for not clarifying it in the question. Lots of good answers here though!
function changeImg(img, i){
img.setAttribute("src", "img/slider/img_" + i + ".jpg");
}
function imgSlider(){
var img = document.createElement("img");
var targetDiv = document.getElementById("slider");
img.setAttribute("width", "100%");
img.setAttribute("height", "70%");
targetDiv.appendChild(img);
for(i=1; i<4; i++){
setInterval(changeImg(img, i), 3000);
}
}

What you need to do is simple, you have to change the setInterval code like this:
$(function () {
var curImg = 1;
setInterval(function () {
$("img").attr("src", "//placehold.it/100?text=" + ++curImg);
}, 2000);
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<img src="//placehold.it/100?text=1" />
Here, I have given an interval of 2 seconds for checking. I have used jQuery only for the updating of image. If you want it in plain JavaScript, it is possible through your code.
Pure JS Version
var curImg = 1;
setInterval(function () {
document.getElementsByTagName("img")[0].src = "//placehold.it/100?text=" + ++curImg;
}, 2000);
<img src="//placehold.it/100?text=1" />

You can do it this way.
Initialize a counter, that will keep a track of current image to being displayed. Now all we need to is call showImage function that will show the image corresponding to the current value of the counter.
Repeat this every 3sec.
var count = 0;
setInterval( function() {
showImage(count);
count = (count+1)%total_no_of_images
}, 3000)

setInterval takes a function, you need to pass it a reference to a function that it will run at the appropriate interval.
Also, note that as of this writing, the accepted answer assumes there are infinite images and has an "infinite loop" style of interval, which should be avoided if at all possible. Here, I stop the clock after the fifth image.
const changeImg = (img, i) => {
img.setAttribute('src', `img/slider/img_${i}.jpg`);
};
const imgSlider = () => {
const img = document.createElement('img');
const targetDiv = document.getElementById('slider');
img.setAttribute('width', '100%');
img.setAttribute('height', '70%');
targetDiv.appendChild(img);
let i = 0;
const interval = setInterval(
() => {
changeImg(img, i);
i += 1;
if (i > 4) {
clearInterval(interval);
}
},
3000
);
};

Change background with a loop without flashing

I am trying to make a changing background. So what I am trying to do is using SetInterval to change my background but whenever it changes, it leaves a white background and then turn to the image like I intend. Any advices on how to fix it?
My code:
var image = new Array();
image.push("url('./1.png')");
image.push("url('./2.png')");
image.push("url('./3.png')");
image.push("url('./4.png')");
image.push("url('./5.png')");
var imagenum = 0;
function changeBackground () {
imagenum++;
if (imagenum==5) {
imagenum = 0;
}
document.getElementById("bodydiv").style.backgroundImage = image[imagenum];
}
function init () {
setInterval(function () {changeBackground()},1000);
}
Bonus: If I set the setInterval a little bit lower, I will have the whole blank site. It works perfectly due to the code, but the flash really irritates me. Can anyone help me with it?

I placed the init() function in the preloadImages() one because it forces init() to only ever run when all images are preloaded. There are other ways to do this however.
var images = new Array();
function preloadImages() {
i=1
foreach(preloadImages.arguments as img)
images[i] = new Image()
images[i].src = img
i++
}
init()
}
function changeBackground () {
imagenum++;
if (imagenum==5) {
imagenum = 0;
}
document.getElementById("bodydiv").style.backgroundImage = image[imagenum];
}
function init () {
setInterval(function () {changeBackground()},1000);
}
var image = [
'./1.png',
'./2.png',
'./3.png',
'./4.png',
'./5.png'
]
preloadImages(image);

How to add prev and next button in slide show

I just made this program for slide show it is working well but i want to use previous and next buttons in the slide show and i don't have any idea how to do that so i put this here please help for the same
var image1=new Image()
image1.src="slide/23.jpg"
var image2=new Image()
image2.src="slide/7.jpg"
var image3=new Image()
image3.src="slide/4.jpg"
var image4=new Image()
image4.src="slide/5.jpg"
var image5=new Image()
image5.src="slide/6.jpg"
</script>
<img id="myImg"src="slide/2.jpg" name="img" width="1000" height="250"/>
<script>
var step=1
function slideImages(){
if (!document.images)
return
document.images.img.src=eval("image"+step+".src")
if (step<5)
step++
else
step=1
setTimeout("slideImages()",3000)
}
slideImages()
</script>

You probably want to abstract away some code so it can be easily reused in your functions:
// Dealing with the counter:
var step;
var steps = 5;
function increment() {
s = (s + 1) % steps;
}
function decrement() {
s--;
if (s<0) s = steps-1;
}
// Dealing with the slide show:
function show() {
document.images.img.src=eval("image"+step+".src")
}
function next() {
increment();
show();
}
function prev() {
decrement();
show();
}
// Automatic sliding:
window.setInterval(next, 3000);
Also, i would reconsider your approach to storing images:
function createImgBySource(src){
var img = new Image();
img.src = src;
return img;
}
var images = [
createImgBySource('slide/23.jpg'),
createImgBySource('slide/7.jpg'),
createImgBySource('slide/4.jpg'),
createImgBySource('slide/5.jpg'),
createImgBySource('slide/6.jpg')
];
Now you can change the increment and decrement functions to use images.length instead of steps, so you can add more images without having to alter other variables. Also, your show() function should look like this (getting rid of the nasty eval):
function show() {
document.images.img.src = images[step];
}

Try the below code
var ss = new TINY.fader.init("ss", {
id: "slides", // ID of the slideshow list container
position: 0, // index where the slideshow should start
auto: 0, // automatic advance in seconds, set to 0 to disable auto advance
resume: true, // boolean if the slideshow should resume after interruption
navid: "pagination", // ID of the slide nav list
activeClass: "current", // active class for the nav relating to current slide
pauseHover: true, // boolean if the slideshow should pause on slide hover
navEvent: "click", // click or mouseover nav event toggle
duration: .25 // duration of the JavaScript transition in seconds, else the CSS controls the duration, set to 0 to disable fading
});
got from Here also here is a sample Fiddle

I would consider using something like jCarousel.

I think you are best putting all of your images into an array and then looking over it. I am assuming that the image tag with the ID 'myImg' is the one that you want to update, as such you should use document.getElementByID('myImg') and not document.images.img.src=eval("image"+step+".src") -- eval should also be avoided as the performance is poor and it can be dangerous.
Put this as the end of your page:
<script type="text/javascript">
(function(){
var step = 0;
var images = [image1, image2, image3, image4, image5];
var image = document.getElementByID('myImg');
var slideImages = function() {
image.src = images[step].src;
step++;
if (step == images.length){
step == 0;
}
setTimeout("slideImages()", 3000);
};
slideImages()
})();
</script>