ES6 Classes & Constructors

class Database {
  async query(sql) {
    console.log(`Executing: ${sql}`);
    // Database logic here
    return [];
  }
}

class DatabaseProxy {
  constructor(database) {
    this.database = database;
    this.cache = new Map();
  }
  
  async query(sql) {
    if (this.cache.has(sql)) {
      console.log('Cache hit');
      return this.cache.get(sql);
    }
    const result = await this.database.query(sql);
    this.cache.set(sql, result);
    return result;
  }
}