coffeeScriptでプライベート変数を使ってみる

private_field

class Car
  _gasoline = 100
  constructor: (@name) ->
  
  run: ->
    _gasoline -= 1
    console.log "#{@name}のガソリン：#{_gasoline}"

track = new Car("トラック")
f1 = new Car("F1")

track.run() # トラックのガソリン：99
f1.run()    # F1のガソリン：98

console.log(track._gasoline) # undefined

private_field.js

// Generated by CoffeeScript 1.10.0
(function() {
  var Car, f1, track;

  Car = (function() {
    var _gasoline;

    _gasoline = 100;

    function Car(name) {
      this.name = name;
    }

    Car.prototype.run = function() {
      _gasoline -= 1;
      return console.log(this.name + "のガソリン：" + _gasoline);
    };

    return Car;

  })();

  track = new Car("トラック");

  f1 = new Car("F1");

  track.run();

  f1.run();

  console.log(track._gasoline);

}).call(this);