test.rb

require 'mini_racer'

ctx = MiniRacer::Context.new
ctx.attach("print", proc {|x| puts x})
ctx.attach("read", proc {|f, type| File.read(f)})
ctx.attach("quit", proc {|status| exit(status)})
ctx.attach("readbuffer", proc {|f| File.read(f).each_char.map(&:to_i)})

#ctx.eval("WebAssembly.instantiate(readbuffer('hello.wasm'), { imports: {} }).then(r => print(999)).catch(e => print('bang'))")
#ctx.eval("1")
#exit

ctx.eval <<~JS
  Module = {
    print: print,
    printErr: function(x) { print("ERR: " + x); }
  }
JS

ctx.eval(File.read('hello.js'))
puts "done"