SOLID Principles in JavaScript

How does this code violate the Dependency Inversion Principle?

class EmailNotifier {
  sendEmail(user, message) {
    // Email sending logic
  }
}

class UserService {
  constructor() {
    this.notifier = new EmailNotifier();
  }

  notifyUser(user, message) {
    this.notifier.sendEmail(user, message);
  }
}

It doesn't use async/await
The class names are not descriptive enough
High-level module depends on low-level module directly
This code violates the Dependency Inversion Principle (DIP). DIP states that high-level modules should not depend on low-level modules; both should depend on abstractions. UserService directly depends on EmailNotifier concrete class. A better approach would be to depend on an INotifier interface, allowing different notification implementations to be injected: email, SMS, push notifications, etc.
It violates single responsibility

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