regexes for fun, and pr... really just for fun

compile.js

function compile(code) {
  code = code.replace(/def\s+([a-zA-Z0-9_$]+)((?:\s[a-zA-Z0-9_$]+)+)\s+=((?:(?!\n\n)[\s\S])+)/g, function (_, functionName, args, functionBody) {
  var functionArgs = args.trim().replace(/\s+/g, ', ');
    return ['function ', functionName, '(', functionArgs, ') {\n  return ', functionBody.trimLeft(), ';}'].join('');
  });
  code = code.replace(/let((?:(?!in)[\s\S])+)in/g, function(_, args) {
    return 'var ' + args.trim() + ';;';
  });
  code = code.replace(/\n[\n]+/g, ';\n');
  code = code.replace(/\n$/g, ';\n');
  code = code.replace(/\s+/g, ' ');
  code = code.replace(/\) ;/g, ');');
  code = code.replace(/;;/g, ';');
  code = code.replace(/; /g, ';');
  code = code.replace(/;([^\n])/g, ';\n$1');
  code = code.replace(/;\s+}/g, ';}');
  return code;
}

/*
for compiling

let
  a = 5,
  b = 6
in
  console.log(a + b) ;;
  let x = 5 in
    def derp y =
      x + y

    console.log(derp(8))
*/