epub3 javascript in Kobo

laverdure · 07-13-2023, 11:43 AM

Hello
I am trying to develo a stupid epub, but a problem arised I cannot solve.
May be someone faced it.

I composed an epub3 using Sigil, with a single HTML page, like this :

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml" xmlns:epub="http://www.idpf.org/2007/ops">
<head>
<title></title>
<script type="text/javascript">
function myFun(k) {
this.item = k;
}
</script>
</head>

<body>
<div id="number_one">
<script type="text/javascript">
const c = new myFun("test");
document.getElementById("number_one").innerHTML = c.item;
</script>
</div>
</body>
</html>

it works fine on any reader I checked, and also on Kobo devices (Aura and Libra).

If I try to use an external file for the function, like this:

xml version="1.0" encoding="utf-8"?>
<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml" xmlns:epub="http://www.idpf.org/2007/ops">
<head>
<title></title>
<script type="text/javascript" src="../Misc/Script0001.js"></script>
</head>

<body>
<div id="number_one">
<script type="text/javascript">
const c = new myFun(" test 01 : from external file");
document.getElementById("number_one").innerHTML = c.item;
</script>
</div>
</body>
</html>

and script Script0001.js :

function myFun(k) {
this.item = k;
}

it works on Thorium, on Adobe Digital, on Sigil previewer but DON'T work on Kobo.

Of course I checked opf, mimetype, etc, etc.
I never got errors, epub checkers say it's fine, but no way.
Could someone help me?
Thanks a lot

DNSB · 07-13-2023, 01:26 PM

The question that comes to mind is if you sent it to your Kobo as a .kepub.epub to trigger the WebKit based renderer. If you send it as an epub, you will use the Adobe RMSDK renderer which is more limited on what it will accept.

laverdure · 07-14-2023, 03:34 AM

Thanks for your answer.
I forgot to state that I made both the tryes.
I used 3 or 4 different tools to translate in kepub (calibre, kepubify, etc.), and the result was always the same of epub: no way!

chrisridd · 07-15-2023, 02:19 AM

Shouldn't your second test use:

Quote:

as this is XML and <script> is an empty element?

Is Script0001.js in the manifest? If you're using Sigil I'd expect it to keeping that up-to-date.

laverdure · 07-15-2023, 07:25 AM

Yes, the file is in the manifest.
I didn’t understand where I should use that script row, sorry.

laverdure · 07-17-2023, 03:48 AM

Hi Chrisridd
I finally got what you said, and I made a try, but the result didn't change.
Thank you for the correction.

chrisridd · 07-17-2023, 04:44 AM

Kobo's a bit ambiguous about their Javascript support on e-ink.

Here it says there's limited support: https://github.com/kobolabs/epub-spe...script-support

But here it says it isn't supported at all: https://github.com/kobolabs/epub-spec#support-grid

laverdure · 07-17-2023, 07:36 AM

Yes, I read that document.
As you can see from my little test, it seems than javascript is supported and working, but it is not if functions are in external files.
I can't undenrstand, external files for fonts and styles are read correctly, so external files js should be read as well...

Quoth · 07-17-2023, 09:06 AM

Quote:

Originally Posted by laverdure

I can't undenrstand, external files for fonts and styles are read correctly, so external files js should be read as well...

JS is very dangerous compared to fonts and styles. It's a good decision that separate files are not supported and a bad one that an ereader supports javascript at all. At the least there should be an on /off setting that by default is off.
Really only non-ereader apps should execute programs.

laverdure · 07-17-2023, 11:16 AM

If someone is interested, I found a way for executing javascript from extern files.
Don't ask me why or what, but I saw that if the epub contains MINIFIED js files, it works correctly on Kobo Aura, Kobo Touch and Kobo Libra.
I made some test on the same epub I posted at the beginning, and on some other file, and the result is OK: if js file is minified it works on Kobo.

chrisridd · 07-19-2023, 12:02 PM

Quote:

Originally Posted by laverdure

if js file is minified it works on Kobo.

Perhaps the file was slightly malformed originally, and minifying has handled that and produced valid output? I have no idea otherwise!

07-13-2023, 11:43 AM	#1
laverdure Junior Member Posts: 9 Karma: 10 Join Date: Feb 2023 Device: kobo h2o	epub3 javascript in Kobo Hello I am trying to develo a stupid epub, but a problem arised I cannot solve. May be someone faced it. I composed an epub3 using Sigil, with a single HTML page, like this : <?xml version="1.0" encoding="utf-8"?> <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml" xmlns:epub="http://www.idpf.org/2007/ops"> <head> <title></title> <script type="text/javascript"> function myFun(k) { this.item = k; } </script> </head> <body> <div id="number_one"> <script type="text/javascript"> const c = new myFun("test"); document.getElementById("number_one").innerHTML = c.item; </script> </div> </body> </html> it works fine on any reader I checked, and also on Kobo devices (Aura and Libra). If I try to use an external file for the function, like this: xml version="1.0" encoding="utf-8"?> <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml" xmlns:epub="http://www.idpf.org/2007/ops"> <head> <title></title> <script type="text/javascript" src="../Misc/Script0001.js"></script> </head> <body> <div id="number_one"> <script type="text/javascript"> const c = new myFun(" test 01 : from external file"); document.getElementById("number_one").innerHTML = c.item; </script> </div> </body> </html> and script Script0001.js : function myFun(k) { this.item = k; } it works on Thorium, on Adobe Digital, on Sigil previewer but DON'T work on Kobo. Of course I checked opf, mimetype, etc, etc. I never got errors, epub checkers say it's fine, but no way. Could someone help me? Thanks a lot

07-17-2023, 11:16 AM	#10
laverdure Junior Member Posts: 9 Karma: 10 Join Date: Feb 2023 Device: kobo h2o	If someone is interested, I found a way for executing javascript from extern files. Don't ask me why or what, but I saw that if the epub contains MINIFIED js files, it works correctly on Kobo Aura, Kobo Touch and Kobo Libra. I made some test on the same epub I posted at the beginning, and on some other file, and the result is OK: if js file is minified it works on Kobo. Last edited by laverdure; 07-17-2023 at 11:17 AM. Reason: Missing info

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07-13-2023, 01:26 PM	#2
DNSB Bibliophagist Posts: 42,588 Karma: 162939992 Join Date: Jul 2010 Location: Vancouver Device: Kobo Sage, Libra Colour, Lenovo M8 FHD, Paperwhite 4, Tolino epos	The question that comes to mind is if you sent it to your Kobo as a .kepub.epub to trigger the WebKit based renderer. If you send it as an epub, you will use the Adobe RMSDK renderer which is more limited on what it will accept.

07-14-2023, 03:34 AM	#3
laverdure Junior Member Posts: 9 Karma: 10 Join Date: Feb 2023 Device: kobo h2o	Thanks for your answer. I forgot to state that I made both the tryes. I used 3 or 4 different tools to translate in kepub (calibre, kepubify, etc.), and the result was always the same of epub: no way!

07-15-2023, 07:25 AM	#5
laverdure Junior Member Posts: 9 Karma: 10 Join Date: Feb 2023 Device: kobo h2o	Yes, the file is in the manifest. I didn’t understand where I should use that script row, sorry.

07-17-2023, 03:48 AM	#6
laverdure Junior Member Posts: 9 Karma: 10 Join Date: Feb 2023 Device: kobo h2o	Hi Chrisridd I finally got what you said, and I made a try, but the result didn't change. Thank you for the correction.

07-17-2023, 04:44 AM	#7
chrisridd Guru Posts: 977 Karma: 2209358 Join Date: Nov 2011 Location: London, UK Device: Kobo Aura, Kobo Aura ONE, PocketBook InkPad Color 3	Kobo's a bit ambiguous about their Javascript support on e-ink. Here it says there's limited support: https://github.com/kobolabs/epub-spe...script-support But here it says it isn't supported at all: https://github.com/kobolabs/epub-spec#support-grid

07-17-2023, 07:36 AM	#8
laverdure Junior Member Posts: 9 Karma: 10 Join Date: Feb 2023 Device: kobo h2o	Yes, I read that document. As you can see from my little test, it seems than javascript is supported and working, but it is not if functions are in external files. I can't undenrstand, external files for fonts and styles are read correctly, so external files js should be read as well...

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