Edit in JSFiddle

//http://www.jermywells.com
//js encapsulation

var Person = function (n,o,g,a) {
    //private variables
    var name = n || '';
    var occupation = o || '';
    var gender = g || '';
    var age = a || '';

    this.toString = function(){
        return JSON.stringify({
            name:name,
            occupation:occupation,
            gender:gender,
            age:age
        });
    }
}

var Gender = {
    male: 'male',
    female: 'female'
}

var jeremy = new Person(
    'Jeremy Wells',
    'Programmer',
    Gender.male, 
    35
);

document.body.innerHTML = jeremy.toString();