Develop Reference

window.onload inconsistent cross-browser?

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)...

IE11 JavaScript (Error: SCRIPT445) "Object doesn't support this action"

I use a Javascript solution which loads the youtube player API asynchronously.
The whole script is supposed to play the video when scrolled to its position.
It works in all browsers and also in IE(11), but sometimes in IE I get an error in Developer Tools: SCRIPT445 (Object doesn't support this action).
The Youtube Player still works but it seems to crash other scripts. I looked around in the web and also here on Stackoverflow. There seem to be others who have similar problems but they were too specific. Maybe someone could help me with this one. Here is the part of the code which makes the problem:
var yt_int, yt_players={},
initYT = function() {
$(".ytplayer").each(function() {
yt_players[this.id] = new YT.Player(this.id); <-- Error line
});
};
$.getScript("//www.youtube.com/player_api", function() {
yt_int = setInterval(function(){
if(typeof YT === "object"){
initYT();
clearInterval(yt_int);
}
},500);
});

object doesn't support this action is error is coming in IE11 using window.dispatchEvent(new Event('resize')); we need to d handle the condition for ie11.
if (navigator.userAgent.indexOf('MSIE') !== -1 || navigator.appVersion.indexOf('Trident/') > 0) {
var evt = document.createEvent('UIEvents');
evt.initUIEvent('resize', true, false, window, 0);
window.dispatchEvent(evt);
} else {
window.dispatchEvent(new Event('resize'));
}

There is a race condition in IE that is firing off your script loader callback before the entire script is evaluated. By using setTimeout(initYT, 0) you will allow the script to finish evaluating before firing your initialization function.

using the video.js api duration call returns 0 while video is much longer

okay So I'm trying to leverage the video.js project as it's seems pretty amazing!
anyways, im writing my first script that interacts with the api which can be found below. it's basically just supposed to output the current play time to the div current_time , the id of video tag is my_stream anyways here's all my javascript ... the problem im having is playLength=0 and current time never updates when video is playing and remains at 0 (ie. is never more then 0 ) im not sure what im doing wrong here ... the api rules i followed can also be found here video.js api docs
function current_time(){
_V_("my_stream").ready(function(){
var myPlayer = this;
// EXAMPLE:
var playLength = myPlayer.duration();
do
{
var position = myPlayer.currentTime();
var myTextArea = document.getElementById('time_count');
myTextArea.innerHTML = position;
}
while(position < playLength);
});
}
window.onload = current_time
anyhelp from any one who's implemented anything with the api or just see something dumb i've done would be greatly appreciated, thanks!

You're assigning the duration to playLength before playback begins. If that's zero when you assign it, it will remain zero. Check the note in the API doc "NOTE: The video must have started loading before the duration can be known, and in the case of Flash, may not be known until the video starts playing."
It looks like you're only concerned about the duration to work out when the video is playing. It would be far better just to use the timeupdate event instead.
var myPlayer;
var myTextArea = document.getElementById('time_count');
videojs('my_stream').ready(function(){
myPlayer = this;
myPlayer.addEvent('timeupdate', onProgress);
});
function onProgress() {
myTextArea.innerHTML = myPlayer.currentTime();
}
This should execute after the DOM has loaded (with window.onload, or jQuery's $(document).ready()), or go in a script tag in the body after the video and #time_count elements.

I Have sort-of solved this problem bymyself by modifying the code I Had written so it now works like so
function current_time(){
_V_("my_stream").ready(function(){
var myPlayer = this;
var playLength = myPlayer.duration();
var position = myPlayer.currentTime();
var myTextArea = document.getElementById('time_count');
myTextArea.innerHTML = position + "/" + playLength;
t=setTimeout(function() {current_time()},2000);
});
}
... although it seems stupid to poll duration continuosly, I actually don't need this value going forward in development, however both populate properly now once the video is playing so it's kinda a solution. I'm not going to except my own answer right away to see if anyone can solve this a better way, or if you can explain why video.js changes the id tag and how to properly deal with it i'll give you an up vote and accept your answer if it all makes sense to me.

Problems preloading audio in Javascript

I'm trying to make a cross-device/browser image and audio preloading scheme for a GameAPI I'm working on. An audio file will preload, and issue a callback once it completes.
The problem is, audio will not start to load on slow page loads, but will usually work on the second try, probably because it cached it and knows it exists.
I've narrowed it down to the audio.load() function. Getting rid of it solves the problem, but interestingly, my motorola droid needs that function.
What are some experiences you've had with HTML5 audio preloading?
Here's my code. Yes, I know loading images in a separate function could cause a race condition :)
var resourcesLoading = 0;
function loadImage(imgSrc) {
//alert("Starting to load an image");
resourcesLoading++;
var image = new Image();
image.src = imgSrc;
image.onload = function() {
//CODE GOES HERE
//alert("A image has been loaded");
resourcesLoading--;
onResourceLoad();
}
}
function loadSound(soundSrc) {
//alert("Starting to load a sound");
resourcesLoading++;
var loaded = false;
//var soundFile = document.createElement("audio");
var soundFile = document.createElement("audio");
console.log(soundFile);
soundFile.autoplay = false;
soundFile.preload = false;
var src = document.createElement("source");
src.src = soundSrc + ".mp3";
soundFile.appendChild(src);
function onLoad() {
loaded = true;
soundFile.removeEventListener("canplaythrough", onLoad, true);
soundFile.removeEventListener("error", onError, true);
//CODE GOES HERE
//alert("A sound has been loaded");
resourcesLoading--;
onResourceLoad();
}
//Attempt to reload the resource 5 times
var retrys = 4;
function onError(e) {
retrys--;
if(retrys > 0) {
soundFile.load();
} else {
loaded = true;
soundFile.removeEventListener("canplaythrough", onLoad, true);
soundFile.removeEventListener("error", onError, true);
alert("A sound has failed to loaded");
resourcesLoading--;
onResourceLoad();
}
}
soundFile.addEventListener("canplaythrough", onLoad, true);
soundFile.addEventListener("error", onError, true);
}
function onResourceLoad() {
if(resourcesLoading == 0)
onLoaded();
}
It's hard to diagnose the problem because it shows no errors and only fails occasionally.

I got it working. The solution was fairly simple actually:
Basically, it works like this:
channel.load();
channel.volume = 0.00000001;
channel.play();
If it isn't obvious, the load function tells browsers and devices that support it to start loading, and then the sound immediately tries to play with the volume virtually at zero. So, if the load function isn't enough, the fact that the sound 'needs' to be played is enough to trigger a load on all the devices I tested.
The load function may actually be redundant now, but based off the inconsistiency with audio implementation, it probably doesn't hurt to have it.
Edit: After testing this on Opera, Safari, Firefox, and Chrome, it looks like setting the volume to 0 will still preload the resource.

canplaythrough fires when enough data has buffered that it probably could play non-stop to the end if you started playing on that event. The HTML Audio element is designed for streaming, so the file may not have completely finished downloading by the time this event fires.
Contrast this to images which only fire their event once they are completely downloaded.
If you navigate away from the page and the audio has not finished completely downloading, the browser probably doesn't cache it at all. However, if it has finished completely downloading, it probably gets cached, which explains the behavior you've seen.
I'd recommend the HTML5 AppCache to make sure the images and audio are certainly cached.

The AppCache, as suggested above, might be your only solution to keep the audio cached from one browser-session to another (that's not what you asked for, right?). but keep in mind the limited amount of space, some browsers offer. Safari for instance allows the user to change this value in the settings but the default is 5MB - hardly enough to save a bunch of songs, especially if other websites that are frequented by your users use AppCache as well. Also IE <10 does not support AppCache.

Alright so I ran into the same problem recently, and my trick was to use a simple ajax request to load the file entirely once (which end into the cache), and then by loading the sound again directly from the cache and use the event binding canplaythrough.
Using Buzz.js as my HTML5 audio library, my code is basically something like that:
var self = this;
$.get(this.file_name+".mp3", function(data) {
self.sound = new buzz.sound(self.file_name, {formats: [ "mp3" ], preload: true});
self.sound.bind("error", function(e) {
console.log("Music Error: " + this.getErrorMessage());
});
self.sound.decreaseVolume(20);
self.sound.bind("canplaythrough",function(){ self.onSoundLoaded(self); });
});

Help making userscript work in chrome

I've written a userscript for Gmail : Pimp.my.Gmail & i'd like it to be compatible with Google Chrome too.
Now i have tried a couple of things, to the best of my Javascript knowledge (which is very weak) & have been successful up-to a certain extent, though im not sure if it's the right way.
Here's what i tried, to make it work in Chrome:
The very first thing i found is that contentWindow.document doesn't work in chrome, so i tried contentDocument, which works.
BUT i noticed one thing, checking the console messages in Firefox and Chrome, i saw that the script gets executed multiple times in Firefox whereas in Chrome it just executes once!
So i had to abandon the window.addEventListener('load', init, false); line and replace it with window.setTimeout(init, 5000); and i'm not sure if this is a good idea.
The other thing i tried is keeping the window.addEventListener('load', init, false); line and using window.setTimeout(init, 1000); inside init() in case the canvasframe is not found.
So please do lemme know what would be the best way to make this script cross-browser compatible.
Oh and im all ears for making this script better/efficient code wise (which im sure is possible)
edit: no help...? :'(
edit 28-Apr:
i re-wrote the code a little and now it looks something like this.:
if(document.location != top.location) return;
(function() {
var interval = window.setInterval(waitforiframe, 3000);
var canvas;
function waitforiframe() {
console.log("Finding canvas frame");
canvas = document.getElementById("canvas_frame");
if (canvas && canvas.contentDocument) {
console.log("Found canvas frame");
pimpmygmail();
}
}
function pimpmygmail() {
gmail = canvas.contentDocument;
if(!gmail) return;
window.clearInterval(interval);
console.log("Lets PIMP.MY.GMAIL!!!");
......rest of the code......
})();
This works perfectly fine in Firefox, but in Chrome, it gives me a top is undefined error.
Another thing i noticed is that if i remove the first line if(document.location != top.location) return; , the waitforiframe() method keeps getting called over and over again. (ie i see the "Finding canvas frame" error in the console)
can someone tell me what does the first line do? i mean what does it achieve & why does the waitforiframe() method run forever if i remove that line??

A BIG THANK YOU TO ALL WHO HELPED! -_- meh
btw, this was all i needed at the beginning of the script:
try { if(top.location.href != window.location.href) { return; } }
catch(e) { return; }