function_juggling.coffee

get = ->
  secret_callback = ( ()-> )
  secret_squirrly_function = ( ()-> secret_callback(err, res, body) )
  # Do something asynchronous
  setTimeout(secret_squirrly_function, 5000)
  # and return a function
  return (
    (callback) ->
      secret_callback = callback
  )

returned_function = get()

returned_function(
  (err, res, body) ->
    console.log "Done!"
)

js_version.js

function get() {
  var secret_callback = function() { };
  var secret_squirrly_function = function() {
    return function() { secret_callback(err, res, body); };
  };
  // Do something asynchronous
  setTimeout(secret_squirrly_function, 5000);
  // and return a function
  return function(callback) {
    secret_callback = callback;
  };
}

returned_function = get();

returned_function(
  function(err, res, body) {
    console.log "Done!";
  }
);