http://jsperf.com/calling-closures/6

commenter.coffee

class Commenter
    constructor: (@author) ->

    write: (message) ->
        console.log "#{@author}: #{message}"

commenter = new Commenter 'Pablo'
commenter.write 'Hello World'

commenter.js

(function() {
  var Commenter, commenter;

  Commenter = (function() {

    function Commenter(author) {
      this.author = author;
    }

    Commenter.prototype.write = function(message) {
      return console.log("" + this.author + ": " + message);
    };

    return Commenter;

  })();

  commenter = new Commenter('Pablo');

  commenter.write('Hello World');

}).call(this);