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Hari 29: Mini Proyek — Type-Safe CRUD

90 min Last updated 09 Apr 2026

Mini Proyek: Type-Safe In-Memory Database

interface Entity { id: number }

class InMemoryDB {
    private store: Map = new Map();
    private nextId = 1;

    insert(data: Omit): T {
        const item = { id: this.nextId++, ...data } as T;
        this.store.set(item.id, item);
        return item;
    }

    findById(id: number): T | undefined {
        return this.store.get(id);
    }

    findAll(predicate?: (item: T) => boolean): T[] {
        const all = [...this.store.values()];
        return predicate ? all.filter(predicate) : all;
    }

    update(id: number, data: Partial>): T | undefined {
        const item = this.store.get(id);
        if (!item) return undefined;
        const updated = { ...item, ...data };
        this.store.set(id, updated);
        return updated;
    }

    delete(id: number): boolean {
        return this.store.delete(id);
    }

    get count(): number { return this.store.size; }
}

interface Mahasiswa extends Entity {
    nama: string;
    jurusan: string;
    ipk: number;
    aktif: boolean;
}

const db = new InMemoryDB();
db.insert({ nama: "Budi",  jurusan: "Informatika",    ipk: 3.75, aktif: true });
db.insert({ nama: "Ani",   jurusan: "Sistem Informasi", ipk: 3.50, aktif: true });
db.insert({ nama: "Cici",  jurusan: "Informatika",    ipk: 3.90, aktif: false });

const informatika = db.findAll(m => m.jurusan === "Informatika" && m.aktif);
console.log(`Informatika aktif: ${informatika.map(m => m.nama).join(", ")}`);
💡 Notice: Setelah delete Keyboard, db.count = 3. Stok rendah < 10: Laptop(5), Mouse(update→5), Monitor(3). Semua 3 produk masuk stok rendah.

Assignment

Implementasikan InMemoryDB untuk Produk {id, nama, harga, stok, kategori}. Insert 4 produk, update 1, delete 1, filter stok < 10, tampilkan.

Expected output:

Stok rendah (3 produk total):
Laptop: 5 unit
Mouse: 5 unit
Monitor: 3 unit
TS index.ts
Solution
Output