I am using the following code to reload a stylesheet when the user makes a selection:
<link type="text/css" id="main_style" href="css/style.php" rel="stylesheet">
<button id="secret_1" style="display:none;"></button>
$(document).ready(function(){
function freshStyle(stylesheet){
$('#main_style').attr('href',stylesheet);
}
$('#secret_1').click(function(event){
event.preventDefault();
var restyled = 'style.php?v='+Math.floor(Math.random() * 10000);
freshStyle(restyled);
});
});
In Chrome, the reload happens fluidly, and the transitions look great. In Firefox, the website temporarily becomes a garbled mess (while the stylesheet is being reloaded) for a second before the new stylesheet is active.
Is this something that can be solved with code, or is this just a feature of the Firefox browser?
If you load the new stylesheet and remove the old one once the new takes effect, the flash of unstyled format should no longer happen
Note: I've done away with jquery inside the .ready since I don't really know how to do a lot of what is happening here in jQuery - vanilla JS all the way for me (but you can convert to jquery if you're more comfortable with it)
$(document).ready(function() {
function freshStyle(stylesheet) {
const id = 'main_style';
const main = document.getElementById(id);
const sibling = main.nextElementSibling;
const parent = main.parentElement;
const style = document.createElement('link');
style.rel = 'stylesheet';
style.href = stylesheet;
style.onload = () => {
// load fires BEFORE style is applied - so delay a tick
setTimeout(() => {
// remove the old stylesheet
main.remove();
// set the id of the new sheet to the removed one
style.id = id;
}, 0);
};
// this just ensures the new stylesheet ends up exactly where the old was
parent.insertBefore(style, sibling);
}
document.getElementById('secret_1').addEventListener('click', (e) => {
e.preventDefault();
const restyled = `style.php?v=${Math.floor(Math.random() * 10000)}`;
freshStyle(restyled);
});
});
I have the below code:
<HTML>
<HEAD>
<SCRIPT>
function myFunction(atlasTrackingURL)
{
var atlasURL = atlasTrackingURL;
if (!atlasURL) return;
//Build a cache busting mechanism
var timestamp = new Date();
var queryString = "?random=" + Math.ceil(Math.random() * 999999999999) +
timestamp.getUTCHours() + timestamp.getUTCMinutes() +
timestamp.getUTCSeconds();
//Build the final URL
atlasURL = atlasURL + queryString;
if (!document.getElementsByTagName || !document.createElement
|| !document.appendChild)
{return false;}
else
{ //Activate the JACTION call
var script = document.createElement("script");
script.type = "text/javascript";
script.src = atlasURL;
document.getElementsByTagName("head")[0].appendChild(script);
return true;
}
}
</SCRIPT>
</HEAD>
<BODY>
Test - Click Me
</BODY>
</HTML>
It works in Internet Explorer every time, but rarely works in Chrome and Firefox. Why would this be?
Can these browsers not handle a function onClick very well? Are there any other options I can take?
I am trying to help a client figure out why one of their tracking tags are not firing off all the time on click in these browsers.
Thanks,
You've got some kind of browser-dependent race condition going on, as Musa pointed out.
Try hiding the link initially, waiting for the document to load, and then adding the onclick attribute and revealing the link with javascript.
So, for example, change the link HTML to something like:
<a id="microsoft-link" href="http://www.microsoft.com" style="display: none;">Test - Click Me</a>
And add in your javascript, below the myFunction(), something like:
document.addEventListener('DOMContentLoaded', function(){
var link_elem = document.getElementById("microsoft-link");
link_elem.onclick = function() {
myFunction('http://view.atdmt.com/jaction/adoakb_PiggybackJSTest_1');
};
link_elem.style.display = 'inherit';
});
jsfiddle -- http://jsfiddle.net/m8VTy/3/
edit: I realized I may be misinterpreting what you're trying to do. What exactly is myFunction() supposed to accomplish ?
I've written a script to test for SVG support in the IMG tag:
function SVGinIMG() {
var SVGdata = 'data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHdpZHRoPSIyNzUiIGhlaWdodD0iMjc1Ij48L3N2Zz4%3D'
var i = document.createElement('img');
i.setAttribute('src',SVGdata);
return i.complete;
}
window.onload = function() {
var hasSVG = SVGinIMG();
alert(hasSVG);
}
This does what I want, except that when I run the script in WebKit browsers the complete property doesn't trigger the first time I load the page; when I refresh the page, it works as it should. The return function is running before the img has finished loading; what's the best method to delay this?
I was complicating things a little; all I really needed was the load event:
function SVGDetect() {
var testImg = 'data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHdpZHRoPSIyNzUiIGhlaWdodD0iMjc1Ij48L3N2Zz4%3D';
var img = document.createElement('img')
img.setAttribute('src',testImg);
img.addEventListener('load',setCSS,true);
}
This runs another function when the image loads, which is never in the case of browsers that don't support SVG in images.
Is there anyway to listen to the onload event for a <link> element?
F.ex:
var link = document.createElement('link');
link.rel = 'stylesheet';
link.href = 'styles.css';
link.onload = link.onreadystatechange = function(e) {
console.log(e);
};
This works for <script> elements, but not <link>. Is there another way?
I just need to know when the styles in the external stylesheet has applied to the DOM.
Update:
Would it be an idea to inject a hidden <iframe>, add the <link> to the head and listen for the window.onload event in the iframe? It should trigger when the css is loaded, but it might not guarantee that it's loaded in the top window...
Today, all modern browsers support the onload event on link tags. So I would guard hacks, such as creating an img element and setting the onerror:
if !('onload' in document.createElement('link')) {
imgTag = document.createElement(img);
imgTag.onerror = function() {};
imgTag.src = ...;
}
This should provide a workaround for FF-8 and earlier and old Safari & Chrome versions.
minor update:
As Michael pointed out, there are some browser exceptions for which we always want to apply the hack. In Coffeescript:
isSafari5: ->
!!navigator.userAgent.match(' Safari/') &&
!navigator.userAgent.match(' Chrom') &&
!!navigator.userAgent.match(' Version/5.')
# Webkit: 535.23 and above supports onload on link tags.
isWebkitNoOnloadSupport: ->
[supportedMajor, supportedMinor] = [535, 23]
if (match = navigator.userAgent.match(/\ AppleWebKit\/(\d+)\.(\d+)/))
match.shift()
[major, minor] = [+match[0], +match[1]]
major < supportedMajor || major == supportedMajor && minor < supportedMinor
This is kind of a hack, but if you can edit the CSS, you could add a special style (with no visible effect) that you can listen for using the technique in this post: http://www.west-wind.com/weblog/posts/478985.aspx
You would need an element in the page that has a class or an id that the CSS will affect. When your code detects that its style has changed, the CSS has been loaded.
A hack, as I said :)
The way I did it on Chrome (not tested on other browsers) is to load the CSS using an Image object and catching its onerror event. The thing is that browser does not know is this resource an image or not, so it will try fetching it anyway. However, since it is not an actual image it will trigger onerror handlers.
var css = new Image();
css.onerror = function() {
// method body
}
// Set the url of the CSS. In link case, link.href
// This will make the browser try to fetch the resource.
css.src = url_of_the_css;
Note that if the resource has already been fetched, this fetch request will hit the cache.
E.g. Android browser doesn't support "onload" / "onreadystatechange" events for element: http://pieisgood.org/test/script-link-events/
But it returns:
"onload" in link === true
So, my solution is to detect Android browser from userAgent and then wait for some special css rule in your stylesheet (e.g., reset for "body" margins).
If it's not Android browser and it supports "onload" event- we will use it:
var userAgent = navigator.userAgent,
iChromeBrowser = /CriOS|Chrome/.test(userAgent),
isAndroidBrowser = /Mozilla\/5.0/.test(userAgent) && /Android/.test(userAgent) && /AppleWebKit/.test(userAgent) && !iChromeBrowser;
addCssLink('PATH/NAME.css', function(){
console.log('css is loaded');
});
function addCssLink(href, onload) {
var css = document.createElement("link");
css.setAttribute("rel", "stylesheet");
css.setAttribute("type", "text/css");
css.setAttribute("href", href);
document.head.appendChild(css);
if (onload) {
if (isAndroidBrowser || !("onload" in css)) {
waitForCss({
success: onload
});
} else {
css.onload = onload;
}
}
}
// We will check for css reset for "body" element- if success-> than css is loaded
function waitForCss(params) {
var maxWaitTime = 1000,
stepTime = 50,
alreadyWaitedTime = 0;
function nextStep() {
var startTime = +new Date(),
endTime;
setTimeout(function () {
endTime = +new Date();
alreadyWaitedTime += (endTime - startTime);
if (alreadyWaitedTime >= maxWaitTime) {
params.fail && params.fail();
} else {
// check for style- if no- revoke timer
if (window.getComputedStyle(document.body).marginTop === '0px') {
params.success();
} else {
nextStep();
}
}
}, stepTime);
}
nextStep();
}
Demo: http://codepen.io/malyw/pen/AuCtH
Since you didn't like my hack :) I looked around for some other way and found one by brothercake.
Basically, what is suggested is to get the CSS using AJAX to make the browser cache it and then treat the link load as instantaneous, since the CSS is cached. This will probably not work every single time (since some browsers may have cache turned off, for example), but almost always.
Another way to do this is to check how many style sheets are loaded. For instance:
With "css_filename" the url or filename of the css file, and "callback" a callback function when the css is loaded:
var style_sheets_count=document.styleSheets.length;
var css = document.createElement('link');
css.setAttribute('rel', 'stylesheet');
css.setAttribute('type', 'text/css');
css.setAttribute('href', css_filename);
document.getElementsByTagName('head').item(0).appendChild(css);
include_javascript_wait_for_css(style_sheets_count, callback, new Date().getTime());
function include_javascript_wait_for_css(style_sheets_count, callback, starttime)
/* Wait some time for a style sheet to load. If the time expires or we succeed
* in loading it, call a callback function.
* Enter: style_sheet_count: the original number of style sheets in the
* document. If this changes, we think we finished
* loading the style sheet.
* callback: a function to call when we finish loading.
* starttime: epoch when we started. Used for a timeout. 12/7/11-DWM */
{
var timeout = 10000; // 10 seconds
if (document.styleSheets.length!=style_sheets_count || (new Date().getTime())-starttime>timeout)
callback();
else
window.setTimeout(function(){include_javascript_wait_for_css(style_sheets_count, callback, starttime)}, 50);
}
This trick is borrowed from the xLazyLoader jQuery plugin:
var count = 0;
(function(){
try {
link.sheet.cssRules;
} catch (e) {
if(count++ < 100)
cssTimeout = setTimeout(arguments.callee, 20);
else
console.log('load failed (FF)');
return;
};
if(link.sheet.cssRules && link.sheet.cssRules.length == 0) // fail in chrome?
console.log('load failed (Webkit)');
else
console.log('loaded');
})();
Tested and working locally in FF (3.6.3) and Chrome (linux - 6.0.408.1 dev)
Demo here (note that this won't work for cross-site css loading, as is done in the demo, under FF)
You either need a specific element which style you know, or if you control the CSS file, you can insert a dummy element for this purpose. This code will exactly make your callback run when the css file's content is applied to the DOM.
// dummy element in the html
<div id="cssloaded"></div>
// dummy element in the css
#cssloaded { height:1px; }
// event handler function
function cssOnload(id, callback) {
setTimeout(function listener(){
var el = document.getElementById(id),
comp = el.currentStyle || getComputedStyle(el, null);
if ( comp.height === "1px" )
callback();
else
setTimeout(listener, 50);
}, 50)
}
// attach an onload handler
cssOnload("cssloaded", function(){
alert("ok");
});
If you use this code in the bottom of the document, you can move the el and comp variables outside of the timer in order to get the element once. But if you want to attach the handler somewhere up in the document (like the head), you should leave the code as is.
Note: tested on FF 3+, IE 5.5+, Chrome
The xLazyLoader plugin fails since the cssRules properties are hidden for stylesheets that belong to other domains (breaks the same origin policy). So what you have to do is compare the ownerNode and owningElements.
Here is a thorough explanation of what todo:
http://yearofmoo.com/2011/03/cross-browser-stylesheet-preloading/
// this work in IE 10, 11 and Safari/Chrome/Firefox/Edge
// if you want to use Promise in an non-es6 browser, add an ES6 poly-fill (or rewrite to use a callback)
let fetchStyle = function(url) {
return new Promise((resolve, reject) => {
let link = document.createElement('link');
link.type = 'text/css';
link.rel = 'stylesheet';
link.onload = resolve;
link.href = url;
let headScript = document.querySelector('script');
headScript.parentNode.insertBefore(link, headScript);
});
};
This is a cross-browser solution
// Your css loader
var d = document,
css = d.head.appendChild(d.createElement('link'))
css.rel = 'stylesheet';
css.type = 'text/css';
css.href = "https://unpkg.com/tachyons#4.10.0/css/tachyons.css"
// Add this
if (typeof s.onload != 'undefined') s.onload = myFun;
} else {
var img = d.createElement("img");
img.onerror = function() {
myFun();
d.body.removeChild(img);
}
d.body.appendChild(img);
img.src = src;
}
function myFun() {
/* ..... PUT YOUR CODE HERE ..... */
}
The answer is based on this link that say:
What happens behind the scenes is that the browser tries to load the
CSS in the img element and, because a stylesheet is not a type of
image, the img element throws the onerror event and executes our
function. Thankfully, browsers load the entire CSS file before
determining its not an image and firing the onerror event.
In modern browsers you can do css.onload and add that code as a fallback to cover old browsers back to 2011 when only Opera and Internet Explorer supported the onload event and onreadystatechange respectively.
Note: I have answered here too and it is my duplicate and deserves to be punished for my honesteness :P
I had written one JS in asp.net. I had called that from body onload, but the JS doesn't get called where I have put my debugger. What could be possible reasons for this? I'm developing website in dotnetnuke.
The JS I have written is syntactically and logically correct.
<script type="text/javascript">
var displayTime, speed, wait, banner1, banner2, link1, link2, bannerIndex, bannerLocations, bannerURLs;
function initVar() {
debugger;
displayTime = 10; // The amount of time each banner will be displayed in seconds.
speed = 5; // The speed at which the banners is moved (1 - 10, anything above 5 is not recommended).
wait = true;
banner1 = document.getElementById("banner1");
banner2 = document.getElementById("banner2");
//link1 = document.getElementById("link1");
//link2 = document.getElementById("link2");
//banner1 = document.getElementById("banner1");
//banner2 = document.getElementById("banner2");
banner1.style.left = 0;
banner2.style.left = 500;
bannerIndex = 1;
/* Important: In order for this script to work properly, please make sure that the banner graphic and the
URL associated with it have the same index in both, the bannerLocations and bannerURLs arrays.
Duplicate URLs are permitted. */
// Enter the location of the banner graphics in the array below.
//bannerLocations = new Array("internet-lg.gif","jupiterweb.gif","jupitermedia.gif");
bannerLocations = new Array("image00.jpg", "image01.jpg", "image02.jpg", "admin_ban.bmp");
// Enter the URL's to which the banners will link to in the array below.
bannerURLs = new Array("http://www.internet.com","http://www.jupiterweb.com","http://www.jupitermedia.com");
}
function moveBanner() {
//debugger;
if(!wait){
banner1.style.left = parseInt(banner1.style.left) - (speed * 5);
banner2.style.left = parseInt(banner2.style.left) - (speed * 5);
if(parseInt(banner1.style.left) <= -500){
banner1.style.left = 500;
bannerIndex = (bannerIndex < (bannerLocations.length - 1)) ? ++bannerIndex :0;
banner1.src = bannerLocations[bannerIndex];
//link1.href = bannerURLs[bannerIndex];
wait = true;
}
if(parseInt(banner2.style.left) <= -500){
banner2.style.left = 500;
bannerIndex = (bannerIndex < (bannerLocations.length - 1)) ? ++bannerIndex :0;
banner2.src = bannerLocations[bannerIndex];
//link2.href = bannerURLs[bannerIndex];
wait = true;
}
setTimeout("moveBanner()",100);
} else {
wait = false;
setTimeout("moveBanner()", displayTime * 1000);
}
}
</script>
REGISTRATION IN JS
<body onload="initVar(); moveBanner();">
</body>
I ran your code. Both methods executed without me having to make any modifications to the posted code. Is there possibly some other code that is overwriting the onload method?
The DotNetNuke best practice for binding to the "onload" property in JavaScript is to hook into JQuery's ready() method:
jQuery(document).ready( function() {
// put your code here
initVar();
moveBanner();
});
DotNetNuke 4.9.x and later ship with the jQuery JavaScript library included.
Have you edited DNN's Default.aspx? Otherwise, there isn't any way for you to have access to the body tag to add the onload attribute like you show.
How are you injecting this script? Are you using a Text/HTML module, are you using the Page Header Text setting for the page, are you adding it directly to the skin, have you written a custom module, or something else?
Instead of using the onload attribute on the body tag, I would suggest wiring up to that event in the script itself. If you're using any code to inject the script, you can ask DNN to register jQuery or a ScriptManager (for ASP.NET AJAX) so that you can use those libraries to wire the event up easily. If you can't guarantee that those are on the page, use the following:
function addLoadEvent(func) {
var oldonload = window.onload;
if (typeof window.onload != 'function') {
window.onload = func;
} else {
window.onload = function() {
if (oldonload) {
oldonload();
}
func();
}
}
}
addLoadEvent(function () {
initVar();
moveBanner();
});
I don't know much about asp.net but if you can put javascript code in your page, then you can try this alternative:
window.onload = function()
{
// any code here
}
This is the same as what you put in body tag.
The CSS left property takes a length, not an integer. You must have units for non-zero lengths. (Even when setting it using JavaScript!).