Private variables and methods in JavaScript and CoffeeScript

private.coffee

Submarine = ->
  # "private", within function scope but not attached to the new instance
  secretWeapon = "missiles"
  fireSecretWeapon = -> console.log "fire ze " + secretWeapon
  # "public", attached to the new instance
  @reveal = -> secretWeapon
  @setWeapon = (weapon) ->
    secretWeapon = weapon
  @fire = -> fireSecretWeapon()
  @

nuclear_submarine = new Submarine
dolphin_submarine = new Submarine
dolphin_submarine.setWeapon "dolphins" # update the "private" var

console.log nuclear_submarine.fire() # => fire ze missiles!
console.log dolphin_submarine.fire() # => fire ze dolphins!
# "Private" functions & vars are "private"
dolphin_submarine.secretWeapon       # => undefined
dolphin_submarine.fireSecretWeapon   # => undefined

private.js

Submarine = function() {
  // "private", within function scope but not attached to the new instance
  var secretWeapon = "missiles";
  var fireSecretWeapon = function() {
    return console.log("fire ze " + secretWeapon);
  }
  // "public", attached to the new instance
  this.reveal = function() {
    return secretWeapon;
  };
  this.setWeapon = function(weapon) {
    return secretWeapon = weapon;
  };
  this.fire = function() {
    return fireSecretWeapon()
  };
  return this;
};

nuclear_submarine = new Submarine;
dolphin_submarine = new Submarine;
dolphin_submarine.setWeapon("dolphins"); // update the "private" var

console.log(nuclear_submarine.fire()) // => fire ze missiles! 
console.log(dolphin_submarine.fire()) // => fire ze dolphins!
// "Private" functions & vars are "private"
dolphin_submarine.secretWeapon        // => undefined
dolphin_submarine.fireSecretWeapon    // => undefined

@danielmurphy points out the the "class definition" has to return this