Basic notes on how to create and inherit objects the crazy-ass JavaScript way.

How to create and inherit objects in JavaScript

/* -------------------------------------------------------
Old-school way to create child objects from parent objects
--------------------------------------------------------*/

var Person = function (name, age, sex) {
    this.name = name;
    this.age = age;
    this.sex = sex;
}
Person.prototype.sayGreeting = function () {
    return 'Hi, my name is ' + this.name + ', my age is ' + this.age + ', and I\'m a ' + this.sex + '.';
}
 
var mom = new Person('Kathy', 40, 'female');
console.log(mom);
console.log(mom.sayGreeting());

// Person {name: "Kathy", age: 40, sex: "female", sayGreeting: function}
// Hi, my name is Kathy, my age is 40, and I'm a female.

var Teenager = function () { }
Teenager.prototype = new Person('Suzy', 20, 'female');
Teenager.prototype.sayCatchPhrase = function () {
    return 'I\'m ' + this.age + ' and I can do what I want.';
}

var daughter = new Teenager();
console.log(daughter);
console.log(daughter.sayGreeting());
console.log(daughter.sayCatchPhrase());

// Teenager {name: "Suzy", age: "20", sex: "female"…}
// Hi, my name is Suzy, my age is 20, and I'm a female.
// I'm 20 and I can do what I want.


/* -------------------------------------------------------
New-school way to create child objects from parent objects
--------------------------------------------------------*/

if (typeof Object.create !== 'function') {
    Object.create = function (o) {
        function F() {}
        F.prototype = o;
        return new F();
    };
}

var mom = {
    name: 'Kathy',
    age: 40,
    sex: 'female',
    sayGreeting: function () {
        return 'Hi, my name is ' + this.name + ', my age is ' + this.age + ', and I\'m a ' + this.sex + '.';
    }
}

// Object {name: "Kathy", age: 40, sex: "female", sayGreeting: function}
// Hi, my name is Kathy, my age is 40, and I'm a female.

var suzy = Object.create(mom);
suzy.name = 'Suzy';
suzy.age = 20;
suzy.sayCatchPhrase = function () {
    return 'I\'m ' + this.age + ' and I can do what I want.';
}

console.log(suzy);
console.log(suzy.sayGreeting());
console.log(suzy.sayCatchPhrase());

// Object {name: "Suzy", age: "20", name: "Kathy", age: 40, sex: "female"…}
// Hi, my name is Suzy, my age is 20, and I'm a female.
// I'm 20 and I can do what I want.


/* --------------------------------
Finding an object's keys and values
---------------------------------*/

for (var key in suzy) {
    console.log(key);
}

// name
// age
// sayCatchPhrase
// sex
// sayGreeting

for (var key in suzy) {
    console.log(suzy[key]);
}

// Suzy
// 20
// function () {
//     return 'I\'m ' + this.age + ' and I can do what I want.';
// }
// female
// function () {
//     return 'Hi, my name is ' + this.name + ', my age is ' + this.age + ', and I\'m a ' + this.sex + '.';
// }