SOLID Principles in JavaScript

What SOLID principle is being violated in this notification system?

class NotificationService {
  sendNotification(message: string, type: string) {
    if (type === 'email') {
      // Send email
    } else if (type === 'sms') {
      // Send SMS
    } else if (type === 'push') {
      // Send push notification
    } else if (type === 'slack') {
      // Send Slack message
    }
  }
}

Open/Closed Principle
This code violates the Open/Closed Principle (OCP). The NotificationService needs to be modified every time a new notification type is added. A better approach would be to define a NotificationStrategy interface and implement different strategies for each notification type. This way, new notification types can be added by creating new strategy classes without modifying existing code.
Single Responsibility Principle
Interface Segregation Principle
Liskov Substitution Principle

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