Does window.onload not work consistently with some browsers..?
I've put a script together purposely utilizing native JavaScript (no library or framework used). I know there may be some issues with cross-browser compatibility. However, there is something different occurring with the Edge browser at least.
The entire page works as expected in webkit(Chrome, not yet in Safari), and it seems to work perfect in the latest Firefox as well.
In Microsoft's Edge browser it seems to have a starter issue, or, it's not booting well every time on the onload trigger. It works perfectly sometimes, if I refresh the page enough.
What can possibly explain this? Edge may be better in this case as I'm not sure if it's working in Safari at all.
Codepen link!
window.onload = function() {
// if you're savvy enough for it... please check codepen for the full code
/* automation from input */
wght_input.oninput = function() {
x = this.value;
var bodyweight = x;
// when puts into form input
this.onchange = function() {
frmFeed[0].innerHTML = "";
recc_wght();
getadd();
whatsTotal();
resetButton.click() ;
};
var kgs = curr_wght_set_amt * kg; //convert lbs lifted to kgs
logs("The highest recorded lift was " + curr_wght_set_amt.toFixed(0) + "lbs or "+ kgs +"kgs");
}; // end active oninput
}; // end onload function
use window.addEventListener instead:
window.addEventListener('load', yourFunc, false);
You'd have to wrap everything else in a named function (yourFunc)...
In a Firefox Add-on SDK add-on, how do I tell whether a window is in the background, ie. visible but not focused?
For example, if I bring a different application to the foreground, the Firefox window becomes unfocused but is still visible.
The reason why I want to do this is because I have a CPU-intensive content script running in the active window, and I'd like to pause it to avoid unnecessary overhead whenever the user isn't actively engaged with the window - meaning it's in the background or minimized.
require("sdk/windows").activeWindow keeps returning the last clicked window even if it's in the background or minimized. There doesn't seem to be any property for the window's focus state.
I can also get use the following code to get an nsIDocShell:
var mostRecentWindow = require("sdk/window/utils").getMostRecentBrowserWindow();
var docShell = require("sdk/window/utils").getWindowDocShell(mostRecentWindow);
Now when I query the docShell.isActive property, it returns true even if the window is in the background.
The one advantage of docShell.isActive is that it returns false when the window is minimized, while activeWindow returns true even in this case. But it's still missing information about whether the window is in the background or not.
Based on the suggestion by #willlma, this code seems to do the trick:
const windows = require('sdk/windows').browserWindows;
const tabs = require("sdk/tabs");
var anyWindowActive = true;
var refreshTimeoutId;
windows.on('deactivate', function(window) {
if (window == windows.activeWindow) {
anyWindowActive = false;
}
clearTimeout(refreshTimeoutId);
refreshTimeoutId = setTimeout(refreshTabStates, 50);
});
windows.on('activate', function(window) {
anyWindowActive = true;
clearTimeout(refreshTimeoutId);
refreshTimeoutId = setTimeout(refreshTabStates, 50);
});
tabs.on('activate', function(tab) {
clearTimeout(refreshTimeoutId);
refreshTimeoutId = setTimeout(refreshTabStates, 50);
});
function refreshTabStates() {
refreshTimeoutId = null;
for (let win of windows) {
for (let tab of win.tabs) {
var shouldBeActive = anyWindowActive
&& tab == tabs.activeTab
&& win == windows.activeWindow;
notifyTab(tab, shouldBeActive);
}
}
}
where notifyTab() is a function that posts a message to that tab's content script (if any) about whether it should be running or not.
setTimeout is used to avoid multiple calls to refreshTabStates in quick succession. For example, if you click on an inactive tab in a window that's not the current one, that one click results in window.deactivate, window.activate and tab.activate events.
Also, the initial state is a problem. What if the user launches Firefox and puts it in the background before any script has managed to run?
I am trying to intercept a sites calls to the window and screen objects from a firefox addon, for their width and height attributes and return my own values .
I have been trying to use an observer
const os = Components.classes["#mozilla.org/observer-service;1"].getService(Components.interfaces.nsIObserverService);
os.addObserver({
observe : function(subject, topic, data) {
if (subject instanceof Ci.nsIDOMWindow && topic == 'content-document-global-created') {
subject.wrappedJSObject.myfunction = function(){
// Do stuff
}
}
}
}, 'content-document-global-created', false);
This allows me to override normal javascript methods but I can't seem to change the screen or window attributes. Would a pagemod be able to modify it with a content script so the site will read the values specified in the addon?
You would do it like this:
subject.wrappedJSObject.screen.__defineGetter__("width", function() { return myWidth });
I'm not sure on the timing as willma pointed out, but this is what the code looks like.
I am opening a popup window and attaching an onbeforeunload event to it like this:
win = window.open("http://www.google.com", "", "width=300px,height=300px");
win.onbeforeunload = function() {
//do your stuff here
alert("Closed");
};
If I leave the URL empty, the new popup opens with "about:blank" as the address but when I close it, I see the alert.
If I open in as you see it (with an external URL), once it's closed, I cannot see the alert anymore. Any idea why this is happening?
As mentioned, same origin policy prevents Javascript from detecting such events. But there's a quite simple solution which allows you to detect closure of such windows.
Here's the JS code:
var openDialog = function(uri, name, options, closeCallback) {
var win = window.open(uri, name, options);
var interval = window.setInterval(function() {
try {
if (win == null || win.closed) {
window.clearInterval(interval);
closeCallback(win);
}
}
catch (e) {
}
}, 1000);
return win;
};
What it does: it creates new window with provided parameters and then sets the checker function with 1s interval. The function then checks if the window object is present and has its closed property set to false. If either ot these is not true, this means, that the window is (probably) closed and we should fire the 'closeCallback function' callback.
This function should work with all modern browsers. Some time ago Opera caused errors when checking properties from windows on other domains - thus the try..catch block. But I've tested it now and it seems it works quite ok.
We used this technique to create 'facebook-style' login popups for sites which doesn't support them via SDK (ehem... Twitter... ehem). This required a little bit of extra work - we couldn't get any message from Twitter itself, but the Oauth redireced us back to our domain, and then we were able to put some data in popup window object which were accessible from the opener. Then in the close callback function we parsed those data and presented the actual results.
One drawback of this method is that the callback is invoked AFTER the window has been closed. Well, this is the best I was able to achieve with cross domain policies in place.
You could listen to the 'focus' event of the opener window which fires when the user closes the popup.
Unfortunately, you're trying to communicate across domains which is prohibited by JavaScript's same origin policy. You'd have to use a server-side proxy or some other ugly hack to get around it.
You could try creating a page on your site that loads the external website in an iframe. You could then pop open that page and listen for it to unload.
I combined #ThomasZ's answer with this one to set an interval limit (didn't want to use setTimeout).
Example (in Typescript, declared anonymously so as not lose reference to "this"):
private _callMethodWithInterval = (url: string, callback: function, delay: number, repetitions: number) => {
const newWindow = window.open(url, "WIndowName", null, true);
let x = 0;
let intervalID = window.setInterval(() => {
//stops interval if newWindow closed or doesn't exist
try {
if (newWindow == null || newWindow.closed) {
console.info("window closed - interval cleared")
callback();
window.clearInterval(intervalID);
}
}
catch (e) {
console.error(`newWindow never closed or null - ${e}`)
}
//stops interval after number of intervals
if (++x === repetitions) {
console.info("max intervals reached - interval cleared")
window.clearInterval(intervalID);
}
}, delay)
}//end _callMethodWithInterval
I can detect when the content of an iframe has loaded using the load event. Unfortunately, for my purposes, there are two problems with this:
If there is an error loading the page (404/500, etc), the load event is never fired.
If some images or other dependencies failed to load, the load event is fired as usual.
Is there some way I can reliably determine if either of the above errors occurred?
I'm writing a semi-web semi-desktop application based on Mozilla/XULRunner, so solutions that only work in Mozilla are welcome.
If you have control over the iframe page (and the pages are on the same domain name), a strategy could be as follows:
In the parent document, initialize a variable var iFrameLoaded = false;
When the iframe document is loaded, set this variable in the parent to true calling from the iframe document a parent's function (setIFrameLoaded(); for example).
check the iFrameLoaded flag using the timer object (set the timer to your preferred timeout limit) - if the flag is still false you can tell that the iframe was not regularly loaded.
I hope this helps.
This is a very late answer, but I will leave it to someone who needs it.
Task: load iframe cross-origin content, emit onLoaded on success and onError on load error.
This is the most cross browsers origin independent solution I could develop. But first of all I will briefly tell about other approaches I had and why they are bad.
1. iframe That was a little shock for me, that iframe only has onload event and it is called on load and on error, no way to know it is error or not.
2. performance.getEntriesByType('resource'). This method returns loaded resources. Sounds like what we need. But what a shame, firefox always adds Resource in resources array no matter it is loaded or failed. No way to know by Resource instance was it success. As usual. By the way, this method does not work in ios<11.
3. script I tried to load html using <script> tag. Emits onload and onerror correctly, sadly, only in Chrome.
And when I was ready to give up, my elder collegue told me about html4 tag <object>. It is like <iframe> tag except it has fallbacks when content is not loaded. That sounds like what we are need! Sadly it is not as easy as it sounds.
CODE SECTION
var obj = document.createElement('object');
// we need to specify a callback (i will mention why later)
obj.innerHTML = '<div style="height:5px"><div/>'; // fallback
obj.style.display = 'block'; // so height=5px will work
obj.style.visibility = 'hidden'; // to hide before loaded
obj.data = src;
After this we can set some attributes to <object> like we'd wanted to do with iframe. The only difference, we should use <params>, not attributes, but their names and values are identical.
for (var prop in params) {
if (params.hasOwnProperty(prop)) {
var param = document.createElement('param');
param.name = prop;
param.value = params[prop];
obj.appendChild(param);
}
}
Now, the hard part. Like many same-like elements, <object> doesn't have specs for callbacks, so each browser behaves differently.
Chrome. On error and on load emits load event.
Firefox. Emits load and error correctly.
Safari. Emits nothing....
Seems like no different from iframe, getEntriesByType, script....
But, we have native browser fallback! So, because we set fallback (innerHtml) directly, we can tell if <object> is loaded or not
function isReallyLoaded(obj) {
return obj.offsetHeight !== 5; // fallback height
}
/**
* Chrome calls always, Firefox on load
*/
obj.onload = function() {
isReallyLoaded(obj) ? onLoaded() : onError();
};
/**
* Firefox on error
*/
obj.onerror = function() {
onError();
};
But what to do with Safari? Good old setTimeout.
var interval = function() {
if (isLoaded) { // some flag
return;
}
if (hasResult(obj)) {
if (isReallyLoaded(obj)) {
onLoaded();
} else {
onError();
}
}
setTimeout(interval, 100);
};
function hasResult(obj) {
return obj.offsetHeight > 0;
}
Yeah.... not so fast. The thing is, <object> when fails has unmentioned in specs behaviour:
Trying to load (size=0)
Fails (size = any) really
Fallback (size = as in innnerHtml)
So, code needs a little enhancement
var interval = function() {
if (isLoaded) { // some flag
return;
}
if (hasResult(obj)) {
if (isReallyLoaded(obj)) {
interval.count++;
// needs less then 400ms to fallback
interval.count > 4 && onLoadedResult(obj, onLoaded);
} else {
onErrorResult(obj, onError);
}
}
setTimeout(interval, 100);
};
interval.count = 0;
setTimeout(interval, 100);
Well, and to start loading
document.body.appendChild(obj);
That is all. I tried to explain code in every detail, so it may look not so foolish.
P.S. WebDev sucks
I had this problem recently and had to resort to setting up a Javascript Polling action on the Parent Page (that contains the IFRAME tag). This JavaScript function checks the IFRAME's contents for explicit elements that should only exist in a GOOD response. This assumes of course that you don't have to deal with violating the "same origin policy."
Instead of checking for all possible errors which might be generated from the many different network resources.. I simply checked for the one constant positive Element(s) that I know should be in a good response.
After a pre-determined time and/or # of failed attempts to detect the expected Element(s), the JavaScript modifies the IFRAME's SRC attribute (to request from my Servlet) a User Friendly Error Page as opposed to displaying the typical HTTP ERROR message. The JavaScript could also just as easily modify the SRC attribute to make an entirely different request.
function checkForContents(){
var contents=document.getElementById('myiframe').contentWindow.document
if(contents){
alert('found contents of myiframe:' + contents);
if(contents.documentElement){
if(contents.documentElement.innerHTML){
alert("Found contents: " +contents.documentElement.innerHTML);
if(contents.documentElement.innerHTML.indexOf("FIND_ME") > -1){
openMediumWindow("woot.html", "mypopup");
}
}
}
}
}
I think that the pageshow event is fired for error pages. Or if you're doing this from chrome, then your check your progress listener's request to see if it's an HTTP channel in which case you can retrieve the status code.
As for page dependencies, I think you can only do this from chrome by adding a capturing onerror event listener, and even then it will only find errors in elements, not CSS backgrounds or other images.
Doesn't answer your question exactly, but my search for an answer brought me here, so I'm posting just in case anyone else had a similar query to me.
It doesn't quite use a load event, but it can detect whether a website is accessible and callable (if it is, then the iFrame, in theory, should load).
At first, I thought to do an AJAX call like everyone else, except that it didn't work for me initially, as I had used jQuery. It works perfectly if you do a XMLHttpRequest:
var url = http://url_to_test.com/
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status != 200) {
console.log("iframe failed to load");
}
};
xhttp.open("GET", url, true);
xhttp.send();
Edit:
So this method works ok, except that it has a lot of false negatives (picks up a lot of stuff that would display in an iframe) due to cross-origin malarky. The way that I got around this was to do a CURL/Web request on a server, and then check the response headers for a) if the website exists, and b) if the headers had set x-frame-options.
This isn't a problem if you run your own webserver, as you can make your own api call for it.
My implementation in node.js:
app.get('/iframetest',function(req,res){ //Call using /iframetest?url=url - needs to be stripped of http:// or https://
var url = req.query.url;
var request = require('https').request({host: url}, function(response){ //This does an https request - require('http') if you want to do a http request
var headers = response.headers;
if (typeof headers["x-frame-options"] != 'undefined') {
res.send(false); //Headers don't allow iframe
} else {
res.send(true); //Headers don't disallow iframe
}
});
request.on('error',function(e){
res.send(false); //website unavailable
});
request.end();
});
Have a id for the top most (body) element in the page that is being loaded in your iframe.
on the Load handler of your iframe, check to see if getElementById() returns a non null value.
If it is, iframe has loaded successfully. else it has failed.
in that case, put frame.src="about:blank". Make sure to remove the loadhandler before doing that.
If the iframe is loaded on the same origin as the parent page, then you can do this:
iframeEl.addEventListener('load', function() {
// NOTE: contentDocument is null if a connection error occurs or if
// X-Frame-Options is not SAMESITE (which could happen with
// 4xx or 5xx error pages if the corresponding error handlers
// do not specify SAMESITE). If error handlers do not specify
// SAMESITE, then networkErrorOccurred will incorrectly be set
// to true.
const networkErrorOccurred = !iframeEl.contentDocument;
const serverErrorOccurred = (
!networkErrorOccurred &&
!iframeEl.contentDocument.querySelector('#well-known-element')
);
if (networkErrorOccurred || serverErrorOccurred) {
let errorMessage;
if (networkErrorOccurred) {
errorMessage = 'Error: Network error';
} else if (serverErrorOccurred) {
errorMessage = 'Error: Server error';
} else {
// Assert that the above code is correct.
throw new Error('networkErrorOccurred and serverErrorOccurred are both false');
}
alert(errorMessage);
}
});