A fork of Simon Holdsworth's JtyOne JavaScript Emulator for the Sinclair ZX81.
Between 2003 and 2006, Mike Wynne wrote a C# emulator, eightyOne for the Sinclair ZX81 that was notable for its realistic rendering of the ZX81's graphics. Unlike most other emulators of the time, Wynne's emulator could reliably render pseudo high-resolution games like Forty-Niner. In 2006, Simon Holdsworth ported the emulator to Java (JtyOne) and in 2015 he ported the emulator to JavaScript.
Why this fork?
Holdsworth's code is quite tightly coupled to the layout of his (excellent) website. For people who want to run a single program, the library is daunting to use. This fork is intended to make it easier to run single ZX81 programs (which must be in TZX format.) This fork now supports to run from a subdirectory. It uses the ZX81X2.ROM version C by Zsolt.
To see the code in action, clone this repo and run
git clone https://github.com/mobluse/zx81js
python -m http.server
and then open http://localhost:8000/zx81js and click on one of the links.
If cloning the repository is too much work, visit mobluse.github.io/zx81js.
You need to convert your TZX files to ASCII hex format and ensure that the resultant file suffix is tzx.hex. You can use, e.g., xxd to do the conversion
xxd -p VU-CALC.tzx | tr -d '\n' > 2.tzx.hex
In the example above 2 is the ID of the ZX81 program (the ID doesn't need to be numeric.)
If you invoke a page running the ZX81 JavaScript emulator with an id query parameter (e.g. http://localhost:8000/zx81js/zx81.html?id=2), the emulator will issue a GET request to the relative URL zx81js/tapes/{id}.tzx.hex.
Looking at the ./ and tapes folders should give you a good idea of what you should do. Of course, you might not want to have static content in a tapes directory; you might prefer to store the TZX "tapes" as binary blobs in an object store or database. No matter how or where you store a TZX archive, it must be returned as ASCII hex when a GET is issued to /zx81js/tapes/{id}.tzx.hex.
The P file format is another common format for ZX81 programs. To convert use the following example in e.g. Debian GNU/Linux 12 (bookworm) aarch64. For Windows a working executable already exists.
cd
git clone https://github.com/mcleod-ideafix/zx81putil
cd zx81putil/
gcc -Wall -O2 zx81putil.c -o zx81putil -lm
cd ~/Downloads/
~/zx81putil/zx81putil aritm-zx81.p -tzx
Use zx81putil, zip, and xxd. Study the zx81stuff web site and this for examples of tracklist.json.