dip.js

/**
 * Dependency Inversion Principle (DIP):
 * High-level modules should not depend directly on low-level modules, 
 * but both should depend on abstractions. Additionally, these abstractions
 * should not depend on details; rather, details should depend on abstractions.
 */

// Bad: High-level module depends on the low-level module's details.
class EmailClient {
    sendEmail() {
      const smtpServer = new SmtpServer();
      smtpServer.connect();
      // Send email logic...
    }
  }
  
class SmtpServer {
    connect() {
        // Connect to SMTP server
    }
}


class SmtpServerV2 {
  connect() {
      // Connect to SMTP server
  }
}


// Good: Both high-level and low-level modules depend on abstractions.
class IEmailServer {
    connect() {}
  }
  
  class SmtpServer extends IEmailServer {
    connect() {
      // Connect to SMTP server
    }
  }
  
  class EmailClient {
    constructor(emailServer) {
      this.emailServer = emailServer;
    }
  
    sendEmail() {
      this.emailServer.connect();
      // Send email logic...
    }
  }
  
  // Usage
  const smtpServer = new SmtpServer();
  const v2 = new SmtpServerV2();
  const emailClient = new EmailClient(smtpServer);
  emailClient.sendEmail();