wasmjs

Simple Python wrapper around QuickJS-NG's qjs-wasi-reactor.wasm.

Quickstart

$ python -m venv my-project
$ source my-project/bin/activate
$ pip install wasmjs
$ python
>>> from wasmjs import wasmjs
>>> js = wasmjs.WasmJS()
>>> js.eval('1 + 2')
3
>>> js.eval('("hello" + "there").toUpperCase()')
'HELLOTHERE'
>>> js.eval('({one: 1, two: 2})')
{'one': 1, 'two': 2}

Structure

qjs-wasi-reactor.wasm is essentially 3 build targets statically linked together:

• QuickJS-NG JavaScript library (JS_Eval, etc.)
• QuickJS-NG qjs CLI tool (qjs_init, etc.)
• Bytecode Alliance wasi-libc C standard library implementation (malloc, etc.)

The API bindings for each component are separated into:

• WasmFile
  • qjs-wasi-reactor.wasm loader. Wraps wasmtime-py, which itself wraps Wasmtime, which is a WebAssembly runtime.
• api.wasilibc
  • malloc that changes the return type of wasi-libc's malloc from an int32 to a uint32, etc.
• api.memutil
  • Convenience functions to get strings and other complex types into and out of the Wasm virtual machine.
• api.qjs
  • JS_Eval that keeps track of the global context, etc.
• api.js
  • Convenience functions to handle all of the multi-step qjs flows.
• jsvalueutil
  • All of the logic needed to get data into and out of the JS virtual machine (inside the Wasm virtual machine).
• WasmJS
  • Convenience layer to simplify all of the above.