Singleton

Ensures a class has only one instance and provides a global point of access to it.

class DatabaseConnection {
  private static instance: DatabaseConnection;
  
  private constructor() {}
  
  public static getInstance(): DatabaseConnection {
    if (!DatabaseConnection.instance) {
      DatabaseConnection.instance = new DatabaseConnection();
    }
    return DatabaseConnection.instance;
  }
  
  public query(sql: string): void {
    console.log(`Executing query: ${sql}`);
  }
}

const db1 = DatabaseConnection.getInstance();
const db2 = DatabaseConnection.getInstance();

console.log(db1 === db2); // true