What is Adapter design pattern?

javascript

// Old system
class OldPaymentGateway {
  processPayment(amount) {
    console.log(`Processing $${amount}`);
  }
}

// New interface needed
class PaymentAdapter {
  constructor(gateway) {
    this.gateway = gateway;
  }
  
  pay(amount, currency) {
    // Adapt old interface to new
    const converted = this.convertCurrency(amount, currency);
    this.gateway.processPayment(converted);
  }
  
  convertCurrency(amount, currency) {
    // Conversion logic
    return amount;
  }
}

// Usage
const oldGateway = new OldPaymentGateway();
const adapter = new PaymentAdapter(oldGateway);
adapter.pay(100, "USD"); // Works with new interface!

Short Answer

Interview ready

Premium

A concise answer to help you respond confidently on this topic during an interview.

Finished reading?

Practice Problems