CYJS

ECMAScript interpreter for Cython & Python built for

• Solving & Decrypting Annoying Puzzles and Captchas at immense speeds.
• Calling upon different Javascript libraries Examples might include:
  • llparse (Even though I maintain a python version but you could easily call upon llparse from javascript using this extension)
  • yt-dlp-ejs (Decrypting challenges might take a while but that was why I wrote this library so we could start optimizing these things )
• Being tiny and easy to use
• Having ECMA6 Support
• Having a maintained backend (QuickJS-NG)
• Being a good companion alongside selectolax or beautiful-soup the choice is yours...
• License friendly, after abandoning pyduktape due to the backend no longer being maintained but also having a pretty poor license all together, It inspired me to try something new for a change that could run newer HTML5 Javascript for any puzzle that is thrown your way.

Installation

Installation of cyjs is pretty simplistic and you can get the released version from pypi

pip install cyjs

Running as a Standalone script

Currently there is a new standalone script if you need to run javascript directly like with quickjs although it currently is in it's early phases. It currently uses typer as a backend (which was developed by the same people who wrote fastapi which is another popular python package).

pip install cyjs[cli]

Using the cli

It should not be difficult although cyjs is still not very mature yet but hopefully the commandline will help to patch a few bugs or make it easier to test different aspects of quickjs-ng.

py -m cyjs -e "console.log('Hello Vizonex');"
Hello Vizonex

Using Unreleased Development Versions

If your planning to contribute or want in on anything newly added you can clone the github repo there is however one dependency needed which is CMake, it was chosen to keep the setuptools section cleansed and allow the quickjs-ng contributors to help us with those sections. You can install cmake using pip if you need something lazy and quick. It's recommended you install cmake globally if you don't have it yet.

pip install cmake

UV (Recommended)

After getting cmake it is recommended to use uv to build and install the cyjs library in development mode

uv sync

Otherwise you can try this approch know that you need pytest if your planning to test anything locally.

uv venv

uv pip install -e .

Alternative Route

pip install -e .

Quick Example

from cyjs import Context, Runtime


def main():
    # You can also provide a runtime if needed it's usage before making multiple contexts however 
    # is completely optional
    rt = Runtime()

    ctx = Context(rt)

    ctx.eval("function add(a, b){ return a + b; }; globalThis.add = add;")
    add_func = ctx.get_global().get("add")

    # 3 
    print(add_func(1, 2))

if __name__ == "__main__":
    main()

Example of use with external html parser tools.

from cyjs import Context
from selectolax.lexbor import LexborHTMLParser

# This example demonstates ways of cracking javascript out of webpages
# with an expernal HTML Parser and cyjs to handle the javascript logic.

# Know that A True HTML5 Dom-API Might require you to make your own 
# functions and imagination but also reverse engineering the target page.

HTML_PAGE = b"""
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
<div class="captcha">
    <script>
function fake_captcha(name) {
    return name + "-key";
}
    </script>
    <!-- Use your imagination a little... -->
</div>
<div>
    <script>
    this.captcha = fake_captcha('123')    
    </script>
</div>
</body>
</html>
"""

def main():
    html = LexborHTMLParser(HTML_PAGE)
    captcha = html.css_first("div.captcha > script").text(strip=True)
    
    fake_solver = Context()
    fake_solver.eval(captcha + "\nglobalThis.fake_captcha = fake_captcha;")
    result = fake_solver.get_global().invoke("fake_captcha", "123")
    # should print
    # "123-key"
    print(result)

if __name__ == "__main__":
    main()

There will be more examples in a future update.

Alternative Python Javascript Interpreters

How to Contribute

There's a few things I didn't get to becuase they are more or less puzzles to implement than they need to be but if anybody can figure these out feel free to fork and send a pull request along with a test added to pytest for eatch to ensure it works correctly. I may be uploading this library to pypi after the other things are implemented but these seem more of a chore for me to solve than really anything else.

• If anybody finds a smarter approch to anything that has already been written throw me an issue or pull request.

• Reporting and fixing bugs.

• JSClass cdef class extension that can be subclassed in python and cython along with the hooks for all the JSClassExoticMethods (we need an approch to passing off a cdef class as an opaque value which I have not figured out how to do yet)

  • JSClassFinalizer Hook
  • JSClassGCMark Hook
  • A safe approch for handling JSClass to python object conversion and vice versa (if possible)