Load all images inside a class - javascript

I am loading 52 images that share the same class, when printing the loaded images to the console the amount of images that are outputting change each time I refresh.
The desired output would be to load every image in the class, as I am trying to tracking the progress with a progress bar then display the image gallery.
var thumbs = document.getElementsByClassName("thumbImg");
var thumbTotal = thumbs.length;
console.log("number of thumbImg's = ", thumbTotal);
$(".thumbImg").on("load", function() {
console.log("the following has loaded = ",this);
});
This outputs the following showing the random amount of images loaded.

May be due to browser caching. You can try checking each image's .complete property, and run the code immediately if already complete.
$(".thumbImg").each(function(i, el) {
if (el.complete) {
handler.call(el);
} else {
$(el).on("load", handler);
}
})
function handler() {
console.log("the following has loaded = ",this);
}

Related

EventListener with delay or fire on load of class

I am tweaking the code of a chrome extension to display the content of a page element in the tab title and scroll it fir navigating open ticket tabs easer. As below
// Need to change this, mousemove listener is super harsh on resource
document.addEventListener("mousemove", function() {
// call the banner element
let bannerTextElements = document.getElementsByClassName("cw_BannerView");
// console.log(bannerTextElements);
// console.log(bannerTextElements[0]);
if (bannerTextElements[0]) {
// console.log("ok");
// console.log(bannerTextElements[0].innerHTML);
// Find and get ticket detail
let bannerTextLine = bannerTextElements[0].getElementsByClassName("detailLabel");
// console.log(bannerTextLine);
if (bannerTextLine[0]) {
// console.log(bannerTextLine[0].innerHTML);
// Trim "Service Ticket for cleanness Need to do this for 'Manage' too"
let tickettext = bannerTextLine[0].innerHTML.split("Manage ");
let tickettext1 = bannerTextLine[0].innerHTML.split("Service Ticket ");
// console.log(tickettext[0]);
// console.log(tickettext[1]);
// Set the title equal to everything after "Service Ticket"
if (tickettext1[1]) {
document.title = tickettext1[1];
// now works!! bit clunky though
var documentTitle = tickettext1 + " - ";
(function titleMarquee() {
document.title = documentTitle = documentTitle.substring(1) +
documentTitle.substring(0,1);
setTimeout(titleMarquee, 160);
})();
} else {
// For everything else, just display what's already there
document.title = tickettext1[0];
}
}
}
}, false);
(ignore the appalling indents i promise thats just on this post! )
However, due to the slow page load the only eventlistener i can get to pick the content of the banner text is 'mousemove' which naturally has the negative side effects of A. Firing infinite times as you view the page and also resetting the scroll to the start as you mouse over.
document.OnLoad and window.onload just stops this working and it loads the default tab title
Is there a way to get onLoad to run after an arbitrary delay, say 10s or to check to make sure that the classname cw_bannerview is loaded up and populate with the ticket title?

Preloading then adding additional images after page load to an image gallery on button click

I am building an image gallery that is populated from a JSON file. Everything works as intended currently, but as of right now there is no pre-loading of content after the initial page load. What I would like to happen is after the "view more" button is clicked I will have some "loading" text show, the batch of images will preload, the "loading" text will disappear, then the images will be added to the page once all items have loaded.
Here is the section of the code that involves the JSON fetch request and the building of elements on the page:
var HTML = '';
var itemsStart = 6; // Starting number of items on page.
var itemsAdd = 9; // Number of items to add to page at a time via button click.
var pItems = document.getElementById('pItems');
var pWrapper = document.getElementById('pItemWrapper');
function addProjects() {
pItems.insertAdjacentHTML('beforeend', HTML);
console.log('BUILD PROJECTS');
}
//Load json
fetch('data/projects.json').then(function (response) {
return response.json();
}).then(function (data){
//Loop through first set of items to load on page.
for (var i = 0; i < itemsStart; i++) {
HTML += '<img src="' + data.projects[i].Image + '" alt=""></img>';
if (i == (itemsStart - 1)) {
addProjects();
}
}
//Load additional items when clicking 'view more'.
document.getElementById('view-more').addEventListener('click', function() {
HTML = '';
for (var i = itemsStart; i < itemsStart + itemsAdd; i++) {
if ((i < data.projects.length)) {
HTML += '<img src="' + data.projects[i].Image + '" alt=""></img>';
}
if (i == ((itemsStart + itemsAdd) - 1) ) {
addProjects();
}
}
itemsStart = itemsStart + itemsAdd;
});
}).catch(function(error) {
console.error('Something went wrong');
});
I'm not using jQuery so I'd like to stick to vanilla js. I don't know what I need to add to my button event listener beyond what I have, I've never tried preloading images like this without using a plugin but I feel like I don't need to load an entire plugin just for this one thing and I'd like to understand how this would work.
EDIT
I feel like I'm almost there, but I still have something wrong. I made some modifications to have each item inside its own container, but instead of that happening I am creating an empty container for each pass of the loop, then the last container gets each image added to it. My code looks like this:
var itemsAdd = 3;
//Load additional items when clicking 'view more'.
document.getElementById('view-more').addEventListener('click', function() {
//The loop will add the next 3 items in the json file per click.
for (var i = itemsStart; i < itemsStart + itemsAdd; i++) {
var placeholder = document.createElement('div');
var src = 'img/portfolio/' + data.projects[i].url;
placeholder.innerHTML= '<div class="img-container">' + data.projects[i].Title + '</div>';
var galleryItem = placeholder.firstChild;
preloadImage(src).then(function (image) {
galleryItem.append(image);
});
pItems.append(galleryItem);
}
itemsStart = itemsStart + itemsAdd;
});
The result I get is this:
Is this because of how the promise works for the preloadImage function?
Generally you would create an image with JavaScript through either document.createElement('img') or the Image() constructor. Both result an in instance of an HTMLImageElement.
With this, you'll have an image that is not connected to the DOM, so it's not visible to you or the user. You can use this element to load the image behind the scenes by setting the image' src property.
Then by listening to the onload event you can determine whenever the image has finished loading. From here you could continue your flow by adding the image to the DOM and, for example, fade it in with animation.
The example below shows this process in the form of a function that returns a Promise. This promise will resolve whenever the load event has been triggered.
const preloadImage = src =>
new Promise(resolve => {
const image = new Image();
const onLoad = () => {
resolve(image);
};
image.addEventListener('load', onLoad, {once: true});
image.src = src;
});
Using it should be like this:
const src = 'http://example.com/my-image.jpg';
preloadImage(src).then(image => {
// Here the image has been loaded and is available to be appended, or otherwise.
document.body.append(image);
});
In your case you would loop over each image, call the function while passing the URL of the image, and append the image to the DOM when it's finished loading.
You can handle any animations, like fade-ins with CSS.
Real world implementation
So how should you implement this in your project? You'll need to start at the point where you create your images. Currently your images are created as strings. But strings are just strings, they aren't HTML elements, yet.
I'd recommend that you'll create a placeholder for each image. This placeholder could visually indicate that an image is loading and act as a wrapper for the image. Add this placeholder immediately to the pItems element.
Then load the image for each Image in your data.projects array by calling the preloadImage. Whenever the image is loaded, append it to the placeholder we've just created. You should now have the effect that first a placeholder is added and the images are starting to appear one by one.
The same logic should be applied for the load more loop.
...
}).then(function (data){
for (let i = 0; i < itemsStart; i++) {
// Create a <div class="placeholder"> which should act as a placeholder / wrapper.
const placeholder = document.createElement('div');
placeholder.classList.add('placeholder');
// Create the image based on the Image value.
// Whenever the image is loaded, add it to the placeholder.
const src = data.projects[i].Image;
preloadImage(src).then(image => {
placeholder.append(image);
});
// Immediately add the placeholder.
// This line doesn't wait for preloadImage to finish because preloadImage is asynchronous. Look into Promises if that is new to you.
pItems.append(placeholder);
}
...
});
From here you've got control over how the placeholder should look and any animations an image inside that placeholder should have.
I think you could put a <div> with black background over the loading image using css and when the image is ready remove it with js. You can detect when the image is loaded using the img.onload = () => {} function.
Or you could place there an img with the loading screen and replace it with the actual image when the image has loaded.

How to find when reportviewer is loaded using reportviewer api

I have created a single page for all my reports and I am loading different versions of those reports (line, pie, chart, graph, etc) with a toolbar I made. All is working well there, except on the non-table type charts (line,pie,bar,etc). When those get rendered, I found that the text in the legends and series become blurry and through some research here and other places found that they are converted to images, which are then getting resized on me though a css class that is auto generated.
Firstly, what i'm trying to do:
I want to remove this class from the image that is generated at the time it is loaded. If i turn off async rendering on my report
AsyncRendering="false"
Along with this bit of jquery (targeting the div that contains the reportviewer):
$(document).ready(function () {
$('#reportDiv img').removeAttr('class');
});
Then the result is as expected. The image is not scaled and all is well. The problem, however, is that some of these reports may be quite large, resulting in the user not having any visual feedback of whether or not something is happening. I would like to continue using async rendering, so I started to look at the reportviewer javascript api.
Sys.Application.add_load(function () {
var reportViewer = $find("ctl00_mainContentPlaceHolder_ReportViewer1");
reportViewer.add_propertyChanged(viewerPropertyChanged);
});
function viewerPropertyChanged(sender, e) {
var viewer = $find("ctl00_mainContentPlaceHolder_ReportViewer1");
if (e.get_propertyName() === "isLoading") {
var button = document.getElementById("ctl00_mainContentPlaceHolder_ctlReportParamModuleId1_btnRunReport");
button.disabled = viewer.get_isLoading();
}
else {
if ($find("ctl00_mainContentPlaceHolder_ReportViewer1").get_reportAreaContent() == Microsoft.Reporting.WebFormsClient.ReportAreaContent.ReportPage) {
alert("here");
}
}
}
The first portion (isLoading) works as expected disabling the button. However immediately upon load I get
Object doesn't support property or method 'get_reportAreaContent'
Am I missing something obvious? These are the links from msdn that I used for reference:
reportviewer isLoading
reportviewer ReportAreaContentType
Bar graphs, Line graphs, pie charts, etc. are rendered as images. The images get re-sized based on the size of the report viewer control. Instead of using AsyncRendering="false", I created this javascript workaround and it has solved my problem.
var app = Sys.Application;
app.add_init(ApplicationInit);
function ApplicationInit(sender) {
var prm = Sys.WebForms.PageRequestManager.getInstance();
if (!prm.get_isInAsyncPostBack()) {
prm.add_endRequest(EndRequest)
}
}
function EndRequest(sender, args) {
var reportViewerControlId = "ReportViewer1";
if (sender._postBackControlClientIDs[0].indexOf(reportViewerControlId) >= 0) {
var reportViewerControlContainer = "reportViewerContainer"; // Id of <DIV>
var renderedReportImage = $("#" + reportViewerControlContainer + " img");
renderedReportImage.removeAttr("style").removeAttr("class");
var styleAttr = renderedReportImage.attr("style");
var classAttr = renderedReportImage.attr("class");
if (typeof styleAttr === 'undefined') {
console.log("Successfully removed the style attribute from the rendered report image!");
}
if (typeof classAttr === 'undefined') {
console.log("Successfully removed the class attribute from the rendered report image!");
}
}
}
Basically, I am listening to the endRequest of the PageRequestManager for my ReportViewerControl's ID, then simply removing the style and class attributes from the image to display it unmodified.

Why does this "loading message" script not work in FF?(javascript)

I have this script which should show the text "Loading..." while images are loading, then change the text to "loaded" when all images are loaded. I added a button to load new images to make sure that it works for dynamically loaded images as well.
This works perfectly in Chrome but in Firefox the "Loading..." text never appears. I have no idea why this would be. The page begins loading and not all images are loaded so it should create the text "Loading.." but it doesn't. Then when all images are done loading the text "Loading" appears.
I just don't get why one message would appear and the other wouldn't. Especially because there are no qualifications that have to be met before creating the "Loading..." text, it should just fire automatically.
jsfiddle Example | Full Page Example
$(document).ready(function() {
var checkComplete = function() {
if($('img').filter(function() {return $('img').prop('complete');}).length == $('img').length) {
$('.status').text('Loaded');
} else {
$('.status').text('Loading...');
}
};
$('img').on('load',function() {
checkComplete();
});
$('#button').click(function() {
$('img.a').attr('src' , 'http://farm9.staticflickr.com/8545/8675107979_ee12611e6e_o.jpg');
$('img.b').attr( 'src' , 'http://farm9.staticflickr.com/8382/8677371836_651f586c99_o.jpg');
checkComplete();
});
checkComplete();
});
You have several issues in the code.
First off, the checkComplete() function is not written correctly. It should be this:
var checkComplete = function() {
var imgs = $('img');
if(imgs.filter(function() {return this.complete;}).length == imgs.length) {
$('.status').text('Loaded');
} else {
$('.status').text('Loading...');
}
};
The main fix here is that the filter callback needs to refer to this.complete, not to $('img').prop('complete') because you are trying to filter a single item at a time.
Second off, you are relying on both .complete and .load working correctly AFTER you've changed the .src value. This is explicitly one of the cases where they do not work properly in all browsers.
The bulletproof way to work around this is to create a new image object for the new images, set the onload handler before you set the .src value and when both onload handlers have fired, you will know that both new images are loaded and you can replace the once you have in the DOM with the new ones.
Here is a version that works in FF:
$(document).ready(function() {
$('#button').click(function() {
var imgA = new Image();
var imgB = new Image();
imgA.className = "a";
imgB.className = "b";
var loaded = 0;
imgA.onload = imgB.onload = function() {
++loaded;
if (loaded == 2) {
$("img.a").replaceWith(imgA);
$("img.b").replaceWith(imgB);
$('.status').text('Loaded');
}
}
// the part with adding now to the end of the URL here is just for testing purposes to break the cache
// remove that part for deployment
var now = new Date().getTime();
imgA.src = 'http://farm9.staticflickr.com/8545/8675107979_ee12611e6e_o.jpg?' + now;
imgB.src = 'http://farm9.staticflickr.com/8382/8677371836_651f586c99_o.jpg?' + now;
$('.status').text('Loading...');
});
});
Working demo: http://jsfiddle.net/jfriend00/yy7GX/
If you want to preserve the original objects, you can use the newly created objects only for preloading the new images and then change .src after they've been preloaded like this:
$(document).ready(function() {
$('#button').click(function() {
var imgA = new Image();
var imgB = new Image();
var loaded = 0;
imgA.onload = imgB.onload = function() {
++loaded;
if (loaded == 2) {
$("img.a")[0].src = imgA.src;
$("img.b")[0].src = imgB.src;
$('.status').text('Loaded');
}
}
// the part with adding now to the end of the URL here is just for testing purposes to break the cache
// remove that part for deployment
var now = new Date().getTime();
imgA.src = 'http://farm9.staticflickr.com/8545/8675107979_ee12611e6e_o.jpg?' + now;
imgB.src = 'http://farm9.staticflickr.com/8382/8677371836_651f586c99_o.jpg?' + now;
$('.status').text('Loading...');
});
});
Working demo of this version: http://jsfiddle.net/jfriend00/ChSQ5/
From the jQuery API .load method
Caveats of the load event when used with images
A common challenge developers attempt to solve using the `.load()` shortcut is to execute a function when an image (or collection of images) have completely loaded. There are several known caveats with this that should be noted. These are:
It doesn't work consistently nor reliably cross-browser
It doesn't fire correctly in WebKit if the image src is set to the same src as before
It doesn't correctly bubble up the DOM tree
Can cease to fire for images that already live in the browser's cache

javascript preloader/progress/percentage

I'm having trouble finding any good information on how to make a javascript(or jquery) progress bar WITH text that tells you the percentage.
I don't want a plug in, I just want to know how it works so that I can adapt it to what I need. How do you preload images and get a variable for the number of images that are preloaded. Also, how do you change html/css and-or call a function, based on the number of images that are loaded already?
<img> elements have an onload event that fires once the image has fully loaded. Therefore, in js you can keep track of the number of images that have loaded vs the number remaining using this event.
Images also have corresponding onerror and onabort events that fire when the image fails to load or the download have been aborted (by the user pressing the 'x' button). You also need to keep track of them along with the onload event to keep track of image loading properly.
Additional answer:
A simple example in pure js:
var img_to_load = [ '/img/1.jpg', '/img/2.jpg' ];
var loaded_images = 0;
for (var i=0; i<img_to_load.length; i++) {
var img = document.createElement('img');
img.src = img_to_load[i];
img.style.display = 'hidden'; // don't display preloaded images
img.onload = function () {
loaded_images ++;
if (loaded_images == img_to_load.length) {
alert('done loading images');
}
else {
alert((100*loaded_images/img_to_load.length) + '% loaded');
}
}
document.body.appendChild(img);
}
The example above doesn't handle onerror or onabort for clarity but real world code should take care of them as well.
What about using something below:
$('#btnUpload').click(function() {
var bar = document.getElementById('progBar'),
fallback = document.getElementById('downloadProgress'),
loaded = 0;
var load = function() {
loaded += 1;
bar.value = loaded;
/* The below will be visible if the progress tag is not supported */
$(fallback).empty().append("HTML5 progress tag not supported: ");
$('#progUpdate').empty().append(loaded + "% loaded");
if (loaded == 100) {
clearInterval(beginLoad);
$('#progUpdate').empty().append("Upload Complete");
console.log('Load was performed.');
}
};
var beginLoad = setInterval(function() {
load();
}, 50);
});
JSFIDDLE
You might also want to try HTML5 progress element:
<section>
<p>Progress: <progress id="p" max=100><span>0</span>%</progress></p>
<script>
var progressBar = document.getElementById('p');
function updateProgress(newValue) {
progressBar.value = newValue;
progressBar.getElementsByTagName('span')[0].textContent = newValue;
} </script>
</section>
http://www.html5tutorial.info/html5-progress.php

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