$3

// Values getters
let valueObject = new ValueObject({ a: 'A', b: 'B' });

valueObject.a(); // --> 'A'
valueObject.b(); // --> 'B'
valueObject.c(); // --> Error, getter does not exist

// Immutability
let valueObject = new ValueObject({ a: { c: 10 }});
valueObject.a().c = 12; // Silent fail, throws in strict mode
valueObject.a(); // --> { c: 10 }

// Change some values, return a new instance
let valueObject = new ValueObject({ a: 'A', b: 'B' });
let newValueObject = valueObject.withValues({ a: 'NEW' })

newValueObject.a(); --> // 'NEW'
newValueObject.b(); --> // 'B'

// Compare by value
let valueObject = new ValueObject({ a: 'A', b: 'B' });
let equalValue = new ValueObject({ a: 'A', b: 'B' });
let differentValue = new ValueObject({ a: 'A', b: 'OTHER' });

console.log(valueObject.equals(equalValue)); // --> true - Equality by value
console.log(valueObject.equals(differentValue)); // --> false - Different values

// Serialize
let valueObject = new ValueObject({ a: 'A', b: 'B' });

console.log(valueObject.serialize()); // --> JSON "{ \"a\": \"A\", \"b\": \"B\" }"
console.log(JSON.stringify(valueObject)) // --> same JSON "{ \"a\": \"A\", \"b\": \"B\" }"

// ==== EXTEND ====
class Email extends ValueObject {

static validators() {
return {
address(address) {
return /^\w+@\w+\..{2,3}(.{2,3})?$/.test(address);
}
};
}

constructor({ address }) {
super({ address });
}

}