JavaScript: Private properties

privileged.js

/* Constructor */
function Klass(text, separator) {

    this.text = text;
    this.separator = separator;

    /* Private properties */
    var _privateField = 'World';
    var _privateMethod = function() {
        return this.separator + _privateField + Klass.staticMethod() + _privateStaticMethod();
    }.bind(this);

    /* Private static properties */
    var _privateStaticMethod = function() {
        return ' =)';
    };

    /* Public properties */
    this.publicMethod = function() {
        return this.text + _privateMethod();
    };
}

/* Public static properties */
Klass.staticMethod = function() {
    return '!';
};

console.log(new Klass('Hello', ', ').publicMethod()); // Hello, World! =)
console.log(Klass.staticMethod()); // !