I need to trigger a piece of code after every single bits are done downloading. The script works if injected after everything is loaded, but how do I trigger that automaticly?
My script is:
var divId = "jwplayer-0_wrapper";
if ($('#' + divId).length == 1) {
myReg = /https?:\/\/www\.youtube\.com\/watch\?v=[^"]+/;
var plainText = $('#' + divId).parent().children('script').text();
var url = plainText.match(myReg);
if (url !== null) {
window.location = url;
};
};
It is used to skip certain site that decide to use the JW player witch I find horribly buggy. So it looks for a div with the indication of the JW player and if there's one, it finds the link to the original youtube video and directly goes there.
Its triggered By Google Chrome Add-on named Javascript Injector and I apply the script on every page I visit. The plug in work perfectly well on sites like www.ayoye.co and www.veuxturire.com. But on other sites, that uses the same pathern, it seems that the script is triggerd too early. For example there www.mondedestars.com and www.lesautos.ca triggers it too early.
If I use the "inject now" fonction of the Add on after the page is really done loading, then it redirects me to the youtube page as expected. I am lost on the why it works some where and not were else.
I'm not trying to understand every single website here, I'd prefer make it dynamicly triggered after the page has done loading everything from its php, ajax, script, flash, html and CSS.
I've tryed to look to the JWplayer API, but since its terribly unclear to me, over the fact that its partialy in flash, it woudl be simpler if there was a way to trigger it after, or maybe just triggering it after i hover over the body, since every sites has a body. It cant be specific to one page.
Use something like this
var timer;
function injectYouTube() {
// DO YOUR STUFF HERE
// ONCE DONE CALL clearInterval(timer);
clearInterval(timer);
}
timer = setInterval(injectYouTube, 2000);
I am not saying this will be called after everything is loaded but instead you can make sure your code is executed when you want it to.
The JWPlayer API are not that difficult. You can retrive the informations you need even not knowing the container id.
This is an example:
var player = jwplayer(0); // get the first jwplayer element of the page
var video = player.getPlaylistItem(); // get the player video
var url = video.file // retrieve the video url
I think the setTimeout or setInterval are unreliable.
Setting up a listener on jwplayer onReady event would be better.
The pessimistic answer to this is that you can't wait until a page has finished all AJAX operations etc. because web pages can continue loading new content indefinitely if they wish.
What you might consider is running your code every time a new HTML element is added to the page. This way, you can be certain to catch JWPlayer the moment it is inserted into the page.
document.addEventListener("DOMNodeInserted", yourRemovalFunction);
Related
I have a GitHub pages site with an image on it. I am trying to have the webpage show an alert whenever I push a change to the website.
My approach so far has been to implement an auto-refresh function:
setTimeout(function(){ location.reload(); }, 60000);
This will auto-update every minute, catching all of the changes that I make. However, I need to show an alert whenever the content of the page changes. It is important to keep in mind that the content will not change upon every refresh -- maybe only every 10 minutes (when I push changes).
I think the way to do this would be to store the name of the image and then look to see if the image name changes at every refresh -- and if the name did change, then show the alert. I have been reading about something called LocalStorage, but I'm not sure how to approach storing the name of a file -- I'm sort of new to JS/HTML.
Is using LocalStorage the best approach to this problem? What are other alternatives/simple ways to implement this on a GitHub page?
Thanks in advance.
If I clearly understand what you need to implement, I'd suggest you to read about MutationObserver in JavaScript. This class tracks all the changes, that are made to binded element. Here's the code and working demo:
<html>
<body>
<p>
Some content
</p>
</body>
<script>
// select the target node
var element = document.getElementsByTagName('p')[0];
// create an observer instance
var observer = new MutationObserver(function(mutations) {
alert("Some changes were made");
});
// configuration of the observer:
var config = { childList: true}; // ,subtree: true, characterData: true
// pass in the target node, as well as the observer options
observer.observe(element, config);
setInterval(function () { // here you can make your changes programatically
element.innerHTML += "New content";
}, 2000)
</script>
</html>
You can also use cookies, i.e. store in a cookie the last "version" of whatever - where "version" can be a string, a number etc.
This has the advantage that it also gets sent to the server, so you may generate the alert layout/code directly on the server.
Check https://github.com/js-cookie/js-cookie for a script simplifying this.
Another alternative is to implement on the server a script that responds whether the content changed. Something like http://foo.bar/changed?lastVer=XXXX which can return a JSON like {changed:true,message:'We have changed the change'}. You would retrieve this via ie. jQuery.getJSON() or vanilla XMLHttpRequest, and if it's the case show the message to the user and then reload the page. But this would require making a runnable server script somewhere.
A third option would be to load the page into, say, a hidden IFRAME, check if the image or content changed and if so transplant only the image - or a certain piece of content - to the main page without refreshing it. Or maybe refresh it. The idea is to load the page in an IFRAME and detect there if something has changed.
I have been trying to create my custom media player using HTML5 and Jquery.
I have followed different approaches and ran into some trouble based on my way of refreshing the page.
First Case
$(document).ready(function(){
duration = Math.ceil($('audio')[0].duration);
$('#duration').html(duration);
});
In this case, the duration returns NaN when I redirect the page to the same URL by pressing the ENTER key in the address bar. However, it works completely fine when I refresh using the reload button or by pressing the F5 button.
Second Case
I read in some answers that loading duration after the loadedmetadataevent might help. So I tried the following:
$(document).ready(function(){
$('audio').on('loadedmetadata', function(){
duration = Math.ceil($('audio')[0].duration);
$('#duration').html(duration);
});
});
Surprisingly, in this case, the inverse of the first case happened. The duration gets displayed completely fine in the case of a redirect, i.e., pressing ENTER while in the address bar. However, in the case of refreshing using the F5 button or the reload button, the duration doesn't get displayed at all, not even NaN which led me to believe that the code doesn't get executed at all.
Further reading suggested this might be a bug within the webkit browsers but I couldn't find anything conclusive or helpful.
What could be the cause behind this peculiar behavior?
It'd be great if you could explain it along with the solution to this problem.
Edit:
I am mainly looking for an explanation behind this difference in behavior. I would like to understand the mechanism behind rendering a page in the case of redirect and refresh.
It sounds like the problem is that the event handler is set too late, i.e. the audio file has loaded its metadata before the document is even ready.
Try setting the event handler as soon as possible by removing the $(document).ready call:
$('audio').on('loadedmetadata', function(){
duration = Math.ceil($('audio')[0].duration);
$('#duration').html(duration);
});
Note that this requires that the <script> tag be after the <audio> tag in the document.
Alternatively, you can tweak your logic slightly, so that the code that updates the duration always runs (but fails gracefully if it gets a NaN):
function updateDuration() {
var duration = Math.ceil($('audio')[0].duration);
if (duration)
$('#duration').html(duration);
}
$(document).ready(function(){
$('audio').on('loadedmetadata', updateDuration);
updateDuration();
});
Lovely code examples and stuff from people - but the explanation is actually very simple.
If the file is already in the cache then the loadedmetadata event will not fire (nor will a number of other events - basically because they've already fired by the time you attach your listeners) and the duration will be set. If it's not in the cache then the duration will be NaN, and the event will fire.
The solution is sort of simple.
function runWhenLoaded() { /* read duration etc, this = audio element */ }
if (!audio.readyState) { // or $audio[0].readyState
audio.addEventListener("loadedmetadata", runWhenLoaded);
// or $audio.on("loadedmetadata", runWhenLoaded);
} else {
runWhenLoaded.call(audio);
// or runWhenLoaded.call($audio[0]);
}
I've included the jQuery alternatives in the code comments.
According to w3 spec this is standard behavior when duration returns NaN.
So I suggest use durationchange event:
$('audio').on('durationchange', function(){
var duration = $('audio')[0].duration;
if(!isNaN(duration)) {
$('#duration').html(Math.ceil(duration));
}
});
NOTE: This code (and your too) will not work correct in case if you have more than one audio element on page. Reason is that you listen events from all audio elements on page and each element will fire own event:
$('audio').on('durationchange', function(){...});
OR
You can try:
<script>
function durationchange() {
var duration = $('audio')[0].duration;
if(!isNaN(duration)) {
$('#duration').html(Math.ceil(duration));
}
}
</script>
<audio ondurationchange="durationchange()">
<source src="test.mp3" type="audio/mpeg">
</audio>
Note that behaviors will differ from one browser to another. On Chrome, you have different type of loading. When resources are not in cache, it will fetch either the complete file (for js or css for example), either a part of the file (mp3 for example). This partial file contains metadata that allows browser to determine duration and other data such as the time it'll take to download whole file at this rate, trigerring for example canplay or canplaythrough events. If you look at network usage in you dev console, you'll see that the HTTP status code will be either 200 (succesful load) or 206(partial load - for mp3 for example).
When you hit refresh, elements are checked to see if they changed. HTTP status will then be 304, meaning file hasn't been modified. If it hasn't changed and is still in browser cache, then it won't be downloaded. The call to determine if it has or not changed comes from the server providing the file.
When ou simply click enter in adress bar, it's automatically taken from cache, not validating online. So it's much faster.
So depending on how you call or refresh your page (either simmple enter, refresh or complete refresh without cache), you'll have big differences on the moment you get the metadata from your mp3. Between taking the metadata from cache directly vs making a request to a server, the difference can be a few hundreds milliseconds, which is enough to change what data is available at different moment.
That being said, listening to loadedmetada should give consistent result. This event is triggered when the data with duration information is loaded, so whatever way the page is loaded, it shouldn't matter if that called is properly made. At this point you have to consider maybe some interference from other elements. What you should do is follow your audio through various events to get exactly where its at at different moments. So in you document ready you could add listeners for different event and see where the problem occurs. Like this:
$('audio')[0].addEventListener('loadstart', check_event)
$('audio')[0].addEventListener('loadeddata', check_event)
$('audio')[0].addEventListener('loadedmetadata', check_event)//at this point you should be able to call duration
$('audio')[0].addEventListener('canplay', check_event) //and so on
function check_event(e) {
console.log(e.target, e.type)
}
You'll see that depending on the way you refresh, these events can come at different moments, maybe explaining inconsistencies in your outputs.
I'm looking for a way to load a website and then check after 1 min or so whether the content has changed, if not, repeat. This is because the website I'm trying to get content from contains javascript for loading the div I need. I thought of using some kind of iFrame, but I have no idea where to start and Google isn't helping me.
Edit
This is the code I'm running with atm and scrapUrl is a defined url so don't worry about it:
var iframe = document.body.appendChild(document.createElement('iframe'));
iframe.src = scrapUrl;
$(iframe).ready(function() {
$(iframe).load(function() {
alert('loaded');
alert($(iframe).contents().find('div#description').html());
});
});
It outputs "loaded" and after that "undefined"
So you're doing a lazy load of content in a div, and you want to know when that div has loaded? Depending how you're doing it, you'd be better to set a flag and react to the AJAX "load" event associated with that lazy load.
If you must do it the way you suggest, try this:
Create an interval (setInterval) that checks the load status, or the contents of the div
if false, do nothing. If true, clearInterval.
So I've made a web app, image below. The app has several tabs which contain different information such as graphs and indicators. The app is made using HTML & Javascript and is one document. I have implemented a Javascript timer which, every 60 seconds, loads the exact same webapp but in a different HTML document, just with different values for the graphs etc. This was just to make it easy for me as i don't have a lot of time at the moment. So every minute the web apps graphs will refresh with different data coming from a different document. So basically i have index.html, index2.html and index3.html, all with the same code/webapp but loading different values into the graphs. Heres the code for the timer:
<script type="text/javascript">
var myVar=setInterval(function(){myTimer()},60000);
$(function () {
});
function myTimer()
{
window.location.replace("index2.html");
}
</script>
The only problem with this is that when, for example, index.html reaches 60 seconds and loads index2.html it goes back to the very first tab (Summary), is there anyway to remain on the same tab even though it's loading a different document?
As #JoshuaM pointed out, the best solution would be to use AJAX, but since you seem mostly satisfied with your current method, you could use a hash on the URL to indicate which tab should be active, e.g.:
index.html#/metrics
index2.html#/metrics
etc...
(I like to put in a leading slash for this sort of thing to distinguish it from a regular anchor link or unexpectedly jumping to an element with the same ID, but in a simple case like this, index.html#metrics could work just as well).
The link for the metrics tab would look like this:
Metrics
(Keep whatever Javascript you have set up on it to make the tabs work.)
Then, when loading the next page, append the hash to it:
var nextPage = 'index2.html';
window.location = nextPage + window.location.hash;
Finally, check for the hash when first loading a page:
var hash = window.location.hash;
//hashes indicating which tab to make active should begin with a slash, e.g. #/metrics
if (hash[1]=='/') {
var currentTab = hash.substr(2);
//activate current tab...
}
Another alternative would be to use an iframe for the graph content but that would probably require more reworking of your code.
So I'd like my page to load content if a window's hash has changed.
Using Mootools, this is pretty easy:
$extend(Element.NativeEvents, {
hashchange: 1
});
and then:
window.addEvent('hashchange', function() {});
However, the hashchange event is firing when the page is being loaded, even though the specification require it not to fire until the page load is complete!
Unless I am loading the page for the first time, with no hash, then all works as expected.
I think the problem here is the fact that the browser considers the page load "complete", and then runs the rest of the JavaScript, which includes hash detection to load the requisite page.
For example, if I typed in http://foo.bar/, all would work fine. However, http://foo.bar/#test would, ideally, load the initial page, detect the hash, and load the "test" content.
Unfortunately, the browser loads the initial page, considers it "domready", and THEN loads the "test" content, which would then fire onHashChange. Oops?
This causes an infinite loop, unless I specifically ask the browser NOT to update the hash if an onHashChange event is firing. That's easy:
var noHashChange;
noHashChange = true;
var hashes = window.location.hash.substr(1).split("/"); // Deciphers the hash, in this case, hashes[0] is "test"
selectContent(hashes[0]); // Here, selectContent would read noHashChange, and wouldn't update the hash
noHashChange = false;
So now, updating the hash AFTER the page has loaded will work properly. Except it still goes nuts on an initial page load and fetches the content about 3 or 4 times, because it keeps detecting the hash has changed. Messy.
I think it may have something to do with how I am setting the hash, but I can't think of a better way to do so except:
window.location.hash = foobar;
... inside of a function that is run whenever new content is selected.
Therein lies the problem, yes? The page is loaded, THEN the content is loaded (if there is content)...
I hope I've been coherent...
Perhaps you could check the hash first to eliminate the recursion:
if(window.location.hash != foobar){ window.location.hash = foobar;}
Why is the onHashChange handler changing the hash anyways? If there's some default that it's selecting first before loading the content, then perhaps that could go in a seperate function.
(I say this because it looks like you've some sort of directory structure-esque convention to your location.hash'es, perhaps you're selecting a specific leaf of a tree when the root is selected or something?)
you could implement an observer for the hash object that will trigger a function when the has object has changed.it does nothing to do with the actual loading of the page.
the best way to do this is via Object.prototype.watch
see other pages on same topic : On - window.location.hash - Change?
have a look at MooTools History it implements the onhashchange if the new html5 history api isn't available, no need to reinvent the wheel :)