mujs

Crystal Lang embedded Javascript interpreter using MuJS.

Example

require "mujs"

js = Mujs.new

js.defn("print", 1) do |args|
  puts args[0].as(String)
end

js.dostring(%[print("hello world")])

more examples at spec/mujs_spec.cr.

Installation

1. Add the dependency to your shard.yml:

   dependencies:
     mujs:
       github: bit4bit/mujs.cr

2. Run shards install

Usage

see spec/mujs_spec.cr

Performance

Benchmarks comparing Crystal native code vs MuJS through Crystal bindings (release mode, Intel i5):

Benchmark	Crystal Native	Through Bindings	Slower By
Function Call (1+2)
Direct Crystal	462.8M ops/s	—	—
Crystal → MuJS (execute JS)	—	9.3M ops/s	49.5x
MuJS → Crystal → MuJS (defn callback)	—	3.3M ops/s	140.6x
Type Conversion - Number	771.3M ops/s	8.6M ops/s	89.8x
Type Conversion - String	751.0M ops/s	4.7M ops/s	159.1x
Type Conversion - Bool	775.6M ops/s	9.1M ops/s	85.6x
Callback (C→JS→C)	761.8M ops/s	3.5M ops/s	218.5x

Key Findings:

• All MuJS calls go through Crystal FFI bindings
• One-way (Crystal→MuJS) is ~2.8x faster than round-trip (MuJS→Crystal→MuJS) (9.3M vs 3.3M ops/s)
• Strings are slowest - 159x slower than native Crystal (most expensive conversion)
• Booleans are fastest - "only" 86x slower than native
• Callbacks are worst - Crossing the boundary twice (C→MuJS→C) costs 218x performance penalty

Run benchmarks yourself:

crystal run benchmark/bench.cr --release --link-flags "-L/home/bit4bit/.local/lib -lmujs -lm"

Development

• Documentation

Contributing

1. Fork it (https://github.com/bit4bit/mujs.cr/fork)
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Contributors

• Jovany Leandro G.C - creator and maintainer