GoF Memento

Memento.js

class Person {
    constructor (name, street, city, state) {
        this.name = name;
        this.street = street;
        this.city = city;
        this.state = state;
    }
    hydrate () {
        const memento = JSON.stringify(this);
        return memento;
    }
    dehydrate (memento) {
        const m = JSON.parse(memento);
        this.name = m.name;
        this.street = m.street;
        this.city = m.city;
        this.state = m.state;
    }
}

class Contacts {
    constructor () {
        this.mementos = {};
    }

    add (key, memento) {
        this.mementos[key] = memento;
    }

    get (key) {
        return this.mementos[key];
    }
}


const anne = new Person("Anne Foley", "1112 Main", "Dallas", "TX");
const john = new Person("John Wang", "48th Street", "San Jose", "CA");
const contacts = new Contacts();

// save state

contacts.add(1, anne.hydrate());
contacts.add(2, john.hydrate());

// mess up their names

anne.name = "King Kong";
john.name = "Superman";

// restore original state

anne.dehydrate(contacts.get(1));
john.dehydrate(contacts.get(2));

console.log(anne.name);
console.log(john.name);

// Anne Foley
// John Wang