Bali

Bali is a work-in-progress JavaScript lexer, parser and interpreter written in Nim that aims to be as compliant as possible to the ECMAScript specifications.
Bali is still not in a usable state yet and is probably unstable. It is not meant to be used in production for now.

I repeat,

Bali is still not in a usable state yet and is probably unstable. It is not meant to be used in production for now.

Usage

• Bali is integrated into the Ferus web engine and used as the JavaScript runtime's backend
• It is integrated into Basket, a fast app launcher for Wayland compositors for configuration.
  Have a cool project that you use Bali in? Open a PR and add it here! :^)

How compliant is it?

Thanks to @CanadaHonk, Bali is now on test262.fyi!
You can check how much Bali progresses/regresses by each day's run.

How fast is it?

With some recent codegen optimizations, Bali is already pretty fast on cherry-picked benchmarks. Bali can perform some optimizations when it is generating code for the provided JavaScript source, granted that it can prove that there is an opportunity to optimize away things.

Iterating 999999999 times and incrementing an integer each loop

Bali has some loop elision optimizations in place which can fully eliminate an expensive loop when it sees the opportunity.
Node is run without a JIT compiler just to be fair to Bali and QuickJS. QuickJS turns out to be the slowest whilst Bali outperforms both of them by a huge margin.

Try it for yourself: Source code

Engine	Time Taken
V8 (Node)	0.521s
Bali	0.012s
QuickJS	27.064s

Finding a substring in a moderately large string

Bali's string-find function (String.prototype.indexOf) is SIMD-accelerated, and as such, is pretty fast. It still gets beaten out by QuickJS, though.

Try it for yourself: Source code

Engine	Time Taken
SpiderMonkey	0.057s
Bali	0.012s
QuickJS	0.003s

Contact Me

You can join the Ferus Discord Server to discuss Bali and other components of the Ferus web engine.

Specification Compliance

As of 9th of November, 2024, Bali can successfully run 1% of the entire Test262 suite* (I believe that our test runner is currently under-estimating). There's a lot of work to be done here, so don't shy away from sending in PRs. ;)

Running code with Bali

You can compile Balde, the Bali debugger by running:

$ nimble build balde

You can run it with no arguments and it'll start up in a REPL.
It is primarily used for debugging the engine as of right now, but it runs code fine too.

Integrating Bali into your applications

Balde requires the C++ backend to be used as it depends on simdutf!

Firstly, add Bali to your project's dependencies.

$ nimble add gh:ferus-web/bali

Here is a basic example of the API:

import bali/grammar/prelude
import bali/runtime/prelude

const JS_SRC = """
console.log("Hello world!")
console.log(13 + 37)

var myUrl = new URL("/~https://github.com/ferus-web/bali")
console.warn(myUrl.origin)

var commitsToBali = 171
while (commitsToBali < 2000) {
    commitsToBali++
    console.log(commitsToBali)
}

let lemonade = fetchLemonade(4)
console.log(lemonade)
"""

let 
  parser = newParser(JS_SRC) # Feed your JavaScript code to Bali's JavaScript parser
  ast = parser.parse() # Parse an AST out of the tokens
  runtime = newRuntime("myfile.js", ast) # Instantiate the JavaScript runtime.

# define a native function which is exposed to the JavaScript code
runtime.defineFn(
    "fetchLemonade",
    proc =
      let num = runtime.ToNumber(&runtime.argument(1))

      if num == 0 or num > 1:
        ret str("You have " & $num & " lemonades!")
      else:
        ret str("You have a lemonade!")
)

# Emit Mirage bytecode and pass over control to the Mirage VM.
# NOTE: This is a blocking function and will block this thread until execution is completed (or an error is encountered and the
# interpreter is halted)
runtime.run()

Roadmap

• Getting a grammar to AST parser [X]
• Getting the MIR emitter working [X]
• Get arithmetic operations working [X]
• Console API [X]
• While loops [X]
• Nested object field access [X]
• typeof [X]
• Arrays [X]
• REPL [X]
• String prototype [X]
• Date prototype [X]
• Ternary operations [X]
• Functions as values [ ]
• For-loops [ ]
• Modules [ ]
• Async [ ]