applyingopenclosed.js

function initializeDatabase(database) {
  if (typeof database.init !== 'function') {
    throw 'Engine has no init method';
  }
  
  database.init();
}

const mySqlEngine = {
  type: 'mysql',
  init: function () {
    // ...
  }
};

const postgresEngine = {
  type: 'postgres',
  init: function () {
    // ...
  }
};
  
initializeDatabase(mySqlEngine);