namedArgs.js

function namedArgs(fn) {
  var names = fn.toString().match(/function.*\(([^\)]+)\)/)[1].split(',');
  return eval("(function(args) {\
    return fn(" + names.map(function(n) { return "args[\"" + n.trim() + "\"]"}).join() + ");\
  })");
}

Converts a javascript function using traditional positional arguments to use named arguments from an object. Argument names are taken from the original declaration.

var ellipse = function(x, y, w, h) {
  // draw ellipse
}

ellipse(30, 40, 10, 20);
ellipse = namedArgs(ellipse);
ellipse({x:20, y:40, w:10, h:20});

Or from coffeescript

ellipse 30, 40, 10, 20
ellipse = namedArgs ellipse
ellipse x:30, y:40, w:10, h:20

Wow.