I'm trying to make an image slider that changes the image 'displayMain' every few seconds. My problem is that when I call the displayMain function in setInterval, I continuously get a 'cannot read property 0 of undefined' error. Even when I use the hardcoded value of jsonData[i].name, I receive the same error. The value gets passed in displayThumbs just fine, however. Does anyone know why I can't retain the values in displayMain but can do so in displayThumbs?
window.addEventListener('load', function () {
var mainDiv = document.getElementById('main');
var descDiv = document.getElementById('main-description');
var gallery = document.querySelector('#main-img');
var ul = document.querySelector('ul');
var li;
var i = 0;
var displayThumbs;
var thumbName;
var current = 0;
var images = [];
function displayMain () {
var data = images[i];
gallery.src = 'img/' + data[0];
descDiv.innerHTML = '<h2>' + data[1] + '</h2>';
}
function displayThumbs () {
for (i = 0; i < images.length; i += 1) {
var data = jsonData[i].name.replace('.jpg', '_thumb.jpg');
// thumbnails use dom to make img tag
li = document.createElement('li');
thumbs[i] = document.createElement('img');
var createThumbNail = thumbs[i].src = 'img/' + data;
thumbs[i].setAttribute('alt', data);
thumbs[i].addEventListener('click', function() {
alert(createThumbNail);
});
ul.appendChild(thumbs[i]);
}
}
// success handler should be called
var getImages = function () {
// create the XHR object
xhr = new XMLHttpRequest();
// prepare the request
xhr.addEventListener('readystatechange', function () {
if (xhr.readyState === 4 && xhr.status == 200) {
// good request ...
jsonData = JSON.parse(xhr.responseText);
for (var i = 0; i < jsonData.length; i += 1) {
var data = [];
data.push(jsonData[i].name);
data.push(jsonData[i].description);
images.push(data);
}
displayMain();
displayThumbs();
setInterval(displayMain, 1000);
}
else {
// error
}
});
xhr.open('GET', 'data/imagedata.json', true);
xhr.send(null);
};
// setInterval(getImages, 2000);
getImages();
// displayThumbs();
});
Your problem is that your displayMain uses whatever value i is at the time, and i never gets incremented, so it'll be equal to images.length after the for loop in displayThumbs. displayThumbs increments it itself, so you won't ever go beyond the end of the array.
In your comment, you mentioned that you want to cycle through the images. This should work a bit better:
function displayMain () {
var data;
// wrap around to the first image
if (i >= images.length) {
i = 0;
}
data = images[i];
gallery.src = 'img/' + data[0];
descDiv.innerHTML = '<h2>' + data[1] + '</h2>';
i++;
}
Personally, I would use a private i, just in case another function reuses the same variable:
function displayMain () {
var data;
// wrap around to the first image
if (displayMain.i >= images.length || isNaN(displayMain.i)) {
displayMain.i = 0;
}
data = images[displayMain.i];
gallery.src = 'img/' + data[0];
descDiv.innerHTML = '<h2>' + data[1] + '</h2>';
// move to the next image
displayMain.i++;
}
This attaches a variable named i to the function displayMain. It will update this variable each time it is called, and no other function will use the same i variable.
Related
I have been playing with this code for a while and I was wondering why when I try to add img’s to the array on the js code makes the images appear on DOM but also makes a bunch of Undefined elements appear, How can I just make the 15 images appear without the undefined? Thanks
enter link description here
var previous = document.getElementById('btnPrevious')
var next = document.getElementById('btnNext')
var gallery = document.getElementById('image-gallery')
var pageIndicator = document.getElementById('page')
var galleryDots = document.getElementById('gallery-dots');
var images = ["https://exoplanets.nasa.gov/internal_resources/1763/",
"https://cdn.britannica.com/56/234056-050-0AC049D7/first-image-from-James-Webb-Space-Telescope-deepest-and-sharpest-infrared-image-of-distant-universe-to-date-SMACS-0723.jpg",
"https://assets.newatlas.com/dims4/default/ac389ce/2147483647/strip/true/crop/1620x1080+150+0/resize/1200x800!/quality/90/?url=http%3A%2F%2Fnewatlas-brightspot.s3.amazonaws.com%2Farchive%2Funiverse-expanding-acceleration-1.jpg",
"https://media.newyorker.com/photos/590966ee1c7a8e33fb38d6cc/master/w_2560%2Cc_limit/Nissan-Universe-Shouts.jpg",
"https://www.thoughtco.com/thmb/NY5k_3slMRttvtS7mA0SXm2WW9Q=/1500x0/filters:no_upscale():max_bytes(150000):strip_icc()/smallerAndromeda-56a8ccf15f9b58b7d0f544fa.jpg",
"https://static.scientificamerican.com/sciam/cache/file/05B8482C-0C04-4E41-859DCCED721883D2_source.jpg?w=590&h=800&7ADE2895-F6E3-4DF4-A11F51B652E9FA88",
"https://qph.cf2.quoracdn.net/main-thumb-66277237-200-huqebnzwetdsnnwvysbxemlskpcxnygf.jpeg",
"http://www.pioneertv.com/media/1090/hero_shot_1080x720.jpg?anchor=center&mode=crop&width=600&height=400&rnd=133159257140000000",
"https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRSWFW1EpMNFM5-dbZEUUnzJkzT3KbUCeuhPHx_eseFCpPeX4Q_DIVPopjS0LeKVmKdQho&usqp=CAU",
"https://cdn.mos.cms.futurecdn.net/rwow8CCG3C3GrqHGiK8qcJ.jpg",
"https://static.wixstatic.com/media/917d103965314e2eacefed92edb6492c.jpg/v1/fill/w_640,h_356,al_c,q_80,usm_0.66_1.00_0.01,enc_auto/917d103965314e2eacefed92edb6492c.jpg",
"https://astronomy.com/~/media/A5B9B6CF36484AB9A6FFAE136C55B355.jpg",
"https://discovery.sndimg.com/content/dam/images/discovery/fullset/2022/9/alien%20planet%20GettyImages-913058614.jpg.rend.hgtvcom.616.411.suffix/1664497398007.jpeg",
"https://images.newscientist.com/wp-content/uploads/2017/06/21180000/planet-10-orange-blue-final-small.jpg?crop=16:9,smart&width=1200&height=675&upscale=true",
"https://images.hindustantimes.com/img/2022/07/20/1600x900/Viral_Instagram_Planet_Rainbow_Nasa_1658316556293_1658316573815_1658316573815.PNG"
]
for (var i = 0; i < 15; i++) {
images.push({
title: "Image " + (i + 1),
source: images[i]
});
}
var perPage = 8;
var page = 1;
var pages = Math.ceil(images.length / perPage)
// Gallery dots
for (var i = 0; i < pages; i++){
var dot = document.createElement('button')
var dotSpan = document.createElement('span')
var dotNumber = document.createTextNode(i + 1)
dot.classList.add('gallery-dot');
dot.setAttribute('data-index', i);
dotSpan.classList.add('sr-only');
dotSpan.appendChild(dotNumber);
dot.appendChild(dotSpan)
dot.addEventListener('click', function(e) {
var self = e.target
goToPage(self.getAttribute('data-index'))
})
galleryDots.appendChild(dot)
}
// Previous Button
previous.addEventListener('click', function() {
if (page === 1) {
page = 1;
} else {
page--;
showImages();
}
})
// Next Button
next.addEventListener('click', function() {
if (page < pages) {
page++;
showImages();
}
})
// Jump to page
function goToPage(index) {
index = parseInt(index);
page = index + 1;
showImages();
}
// Load images
function showImages() {
while(gallery.firstChild) gallery.removeChild(gallery.firstChild)
var offset = (page - 1) * perPage;
var dots = document.querySelectorAll('.gallery-dot');
for (var i = 0; i < dots.length; i++){
dots[i].classList.remove('active');
}
dots[page - 1].classList.add('active');
for (var i = offset; i < offset + perPage; i++) {
if ( images[i] ) {
var template = document.createElement('div');
var title = document.createElement('p');
var titleText = document.createTextNode(images[i].title);
var img = document.createElement('img');
template.classList.add('template')
img.setAttribute("src", images[i].source);
img.setAttribute('alt', images[i].title);
title.appendChild(titleText);
template.appendChild(img);
template.appendChild(title);
gallery.appendChild(template);
}
}
// Animate images
var galleryItems = document.querySelectorAll('.template')
for (var i = 0; i < galleryItems.length; i++) {
var onAnimateItemIn = animateItemIn(i);
setTimeout(onAnimateItemIn, i * 100);
}
function animateItemIn(i) {
var item = galleryItems[i];
return function() {
item.classList.add('animate');
}
}
// Update page indicator
pageIndicator.textContent = "Page " + page + " of " + pages;
}
showImages();
I checked your code and make it work with a small modification.
You are reusing the same array with the links of images and push inside the new object with the shape of { title, source }.
You just need to do this changes:
Change the name of your array of images. Something from images to arrayOfImages.
const arrayOfImages = ["https://exoplanets.nasa.gov/internal_resources/1763/", ...]
Declare an empty array before your first for loop. Make something like const images = []
On your for loop, instead of loop over the images variable, do it over the arrayOfImages variable.
const images = [];
for (var i = 0; i < 15; i++) {
images.push({
title: "Image " + (i + 1),
source: arrayOfImages[i]
});
}
With those changes, everything works for me.
Also, as a recommendation, try to avoid the var keyword. If you want more details about this, this answer is very helpful: https://stackoverflow.com/a/50335579/17101307
You can use Array#map to create a new array of objects from the array of URLS, then replace the original array.
images = images.map((x, i) => ({
title: "Image " + (i + 1),
source: x
}));
I'm trying to create a lightbox for my site, and I want it to load all the images from a given directory with a filename like image#.jpg.
This is the code I have:
for(var i=0; i<1000; i++)
{
var filename = "images/image"+i+".jpg";
$.get(filename)
.done(function() {
$('#lightbox').append('<img src="placeholder.gif">');
})
.fail(function() {
i=1000; //ugh
});
}
It kind of works, but only tries to load image1000.jpg.
Also, is there a better way to do something like this? I'm sure saying 'do this a ton of times and stop when I manually change the for loop counter' is frowned on.
If your image names are sequential like your said, you can create a loop for the names, checking at every iteration if image exists - and if it doesn't - break the loop:
var bCheckEnabled = true;
var bFinishCheck = false;
var img;
var imgArray = new Array();
var i = 0;
var myInterval = setInterval(loadImage, 1);
function loadImage() {
if (bFinishCheck) {
clearInterval(myInterval);
alert('Loaded ' + i + ' image(s)!)');
return;
}
if (bCheckEnabled) {
bCheckEnabled = false;
img = new Image();
img.onload = fExists;
img.onerror = fDoesntExist;
img.src = 'images/myFolder/' + i + '.png';
}
}
function fExists() {
imgArray.push(img);
i++;
bCheckEnabled = true;
}
I've been trying to create a small HTML5-based example, but I've ran into some problems. I want to render a rock on a <canvas> but this Javascript object won't work properly.
function ImageData() {
this.image_names = ["rock1"];
this.images = new Array();
this.loadResources = function () {
for (var i = 0; i < this.image_names.length; i++) {
var img = new Image();
img.onload = (function (a) {
a.images[a.image_names[i]] = img;
console.log(a.images); //log is successful, image is in array
})(this);
img.src = "images/" + this.image_names[i] + ".png";
}
}
}
It's use is to be as follows:
var a = new ImageData();
a.loadResources();
var rock1_image = a.images["rock1"]; //the "rock1.png" image
If you try accessing the object via console, you'll see that there is no image in the image array, after being certain the image loaded. I can't figure out why it's not working. I've looked over it multiple times.
EDIT: Here is my final, working result:
function ImageData() {
this.image_names = ["rock1"];
this.images = new Array();
this.loadResources = function (callback) {
for (var i = 0; i < this.image_names.length; i++) {
var img = new Image();
img.onload = (function (a, i) {
return function() {
a.images[a.image_names[i]] = img;
if (i == (a.image_names.length - 1)) callback();
};
})(this, i);
img.src = "images/" + this.image_names[i] + ".png";
}
}
}
I would venture to say that you are attempting to access it before it is added to your array. I would suggest adding a callback or something to your loadResources method to make sure that it's there before you attempt to access it.
this.loadResources = function (callback) {
for (var i = 0; i < this.image_names.length; i++) {
var img = new Image();
img.onload = (function (a, i) {
return function() {
a.images[a.image_names[i]] = img;
console.log(a.images); //log is successful, image is in array
callback();
};
})(this, i);
img.src = "images/" + this.image_names[i] + ".png";
}
}
then
var a = new ImageData();
var rock1_image;
a.loadResources(function() {
rock1_image = a.images["rock1"];
// do whatever you need to do with the image in here.
});
Also, what #Igor mentions. I totally missed that. I adjusted the code above so you could keep your this scope without having to set it elsewhere.
Updated to take care of the i issue brought up by #RobD.
Remove (this) after onload handler definition. You are actually calling this function right away, assigning undefined (since it returns nothing) as img.onload value.
In the code:
> function ImageData() {
> this.image_names = ["rock1"];
> this.images = new Array();
> this.loadResources = function () {
> for (var i = 0; i < this.image_names.length; i++) {
> var img = new Image();
> img.onload = (function (a) {
This function will be run immediately and does not return a value, so undefined will be assigned. So no point in the assignment, just run the code.
> a.images[a.image_names[i]] = img;
Images is an array that is used as a plain object. Better to use a plain object then.
> console.log(a.images); //log is successful, image is in array
> })(this);
The outer this must be passed in because of the IIFE. Remove the IIFE and there is no requirement to pass this. And if a reference to the instance is stored in the function, it won't matter how the function is called (i.e. you won't have to set this in the call).
> img.src = "images/" + this.image_names[i] + ".png";
> }
> }
> }
You might want something like:
function ImageData() {
this.image_names = ['rock1'];
this.images = {};
imageData = this;
this.loadResources = function (callback) {
for (var i = 0; i < imageData.image_names.length; i++) {
var img = new Image();
imageData.images[a.image_names[i]] = img;
img.src = 'images/' + this.image_names[i] + '.png';
if (callback) {
img.onload = callback;
}
}
}
}
var a = new ImageData();
a.loadResources(function(){console.log('loaded: ' + this.src);}); // loaded: …
window.onload = function() {
document.body.appendChild(a.images.rock1); // image appears in document
}
I haven't tested your code yet, but I guess this is the problem:
You are trying to access your image before it was loaded. You can use callback event handler after it was load like:
var data = new ImageData();
data.loadResources(function(imgObj){
// imgObj is the newly load image here. Have fun with it now!
})
I am trying to call two functions when only the "add" button is clicked. the problem I am having is that the final four textboxes in the calculate_balances function are not outputting their variables.
var $ = function (id) {
return document.getElementById(id);
}
// Declare Arrays to store information from Inputs //
var transactions = [];
transactions[0] = []; // holds date
transactions[1] = []; // holds transaction type
transactions[2] = []; // holds amount
// Function to print results to text area //
var update_results = function () {
var list = ""; // string variable to build output //
// check to see if arrays are empty //
if (transactions[0].length == 0) {
$("results").value = "";
} else {
list = "";
// for loop to cycle through arrays and build string for textarea output //
for (var i = 0; i < transactions[0].length; i++) {
list += transactions[0][i] + " " + transactions[1][i] + " " + transactions[2][i] + "\n";
}
// display results //
$("results").value = list;
}
}
// function to gather inputs //
var add_transaction = function () {
$("add").blur();
transactions[0][transactions[0].length] = $("date").value;
transactions[1][transactions[1].length] = $("transType").value;
transactions[2][transactions[2].length] = parseFloat( $("amount").value);
update_results();
calculate_balances();
}
// function for Calculations //
var calculate_balances = function () {
var startBal = 2000.00;
var ttlDeposits = 0;
var ttlWithdrawals = 0;
var endBal = startBal;
if (transactions[1][transactions[1].length] == "deposit")
{
ttlDeposits += transactions[2][transactions[2].length];
endBal += ttlDeposits;
}
if (transactions[1][i] == "withdrawal")
{
ttlWithdrawals += transactions[2][transactions[i]];
endBal -= ttlWithdrawals;
}
$("balStart").value = parseFloat(startBal);
$("ttlDeposits").value = parseFloat(ttlDeposits);
$("ttlWithdrawals").value = parseFloat(ttlWithdrawals);
$("balEnd").value = parseFloat(endBal);
}
window.onload = function () {
$("add").onclick = add_transaction, calculate_balances;
update_results();
}
tHank you
Edit: Did not realize the OP was NOT using jQuery. Your onclick should look like this:
$("add").onclick = function(){
add_transaction();
calculate_balances();
};
The rest here is for jQuery which is not what the OP wanted.
For setting the value of a text box with jQuery use the val() method:
$("balStart").val(parseFloat(startBal));
To call the two methods when the button is clicked:
$("add").click(function(){
add_transaction();
calculate_balances();
});
I have a problem with putting a variable into my array. Here is my code:
var info = new Array();
google.load("feeds", "1");
function initialize() {
var feed = new google.feeds.Feed("http://www.ntvmsnbc.com/id/24927681/device/rss/rss.xml");
feed.setNumEntries(6);
feed.load(function(result) {
if (!result.error) {
var container = document.getElementById("feed");
var html = '';
for (var i = 0; i < result.feed.entries.length; i++) {
var entry = result.feed.entries[i];
var a = " " ;
a += entry.title;
info[i] = a
html += '<p>' + entry.publishedDate + ' ' + entry.title;
}
container.innerHTML = html;
}
alert(info[0]);
});
//alert(info[0]);
}
//alert(info[0]);
google.setOnLoadCallback(initialize);
You see an array called info. I'm trying to add entry.title into it. You can see some places are commented out. There my info[0] is empty. I can display my result only in function(result), except that it doesn't display anything like I never put anything inside my array. I didn't understand why.
Updated:
var info = new Array();
google.load("feeds", "1");
function initialize(cb) {
var feed = new google.feeds.Feed("http://www.ntvmsnbc.com/id/24927681/device/rss/rss.xml");
feed.setNumEntries(6);
feed.load(function(result) {
if (!result.error) {
var container = document.getElementById("feed");
var html = '';
for (var i = 0; i < result.feed.entries.length; i++) {
var entry = result.feed.entries[i];
html += '<p>' + entry.publishedDate + ' ' + entry.title;
cb(entry.title);
}
container.innerHTML = html;
}
});
}
google.setOnLoadCallback(function(){
initizalize(processInfo);}
);
function processInfo(information){
info[info.length] = information;
alert(info[info.length]);
}
Last Version
var info = new Array();
google.load("feeds", "1");
function initialize(cb) {
var feed = new google.feeds.Feed("http://www.ntvmsnbc.com/id/24927681/device/rss/rss.xml");
feed.setNumEntries(6);
feed.load(function(result) {
if (!result.error) {
var container = document.getElementById("feed");
var html = '';
for (var i = 0; i < result.feed.entries.length; i++) {
var entry = result.feed.entries[i];
var a= " ";
a += entry.title;
info[i] = a;
html += '<p>' + entry.publishedDate + ' ' + entry.title;
}
container.innerHTML = html;
}
cb(info);
});
}
google.setOnLoadCallback(function(){
initizalize(processInfo);}
);
function processInfo(info){
alert(info[0]);
}
That's because AJAX is Asynchronous, basically meaning it won't run until at least the rest of the code has been run. Anything that relies on stuff that's defined an an AJAX call (or any other asynchronous callback) MUST be inside that callback, or itself deferred until later.
Make sure result.feed.entries.length is non-zero and that you are actually executing the for loop. Also (but minor) it wouldn't hurt to have a ; after the info[i] = a
You can't display info in those points because the call to feed.load() is asynchronous, and hasn't finished by that point.
You need to make all processing continue in the .load callback function, e.g. something like:
function initialize(cb) {
feed.load(function(result) {
...
cb(info); // only call the callback once the data is loaded
});
}
// call the above function, passing a callback handler
google.setOnLoadCallback(function() {
initialize(processInfo);
}));
// defer all of your data processing to here
function processInfo(info) {
...
}