• Para excluir um favorito precisaremos de um método no serviço:

// src/services/favoriteService.ts

import { Favorite } from "../models/favorite"

export const favoriteService = {

// ...

  },

  delete: async (userId: number, courseId: number) => {
    await Favorite.destroy({
      where: {
        userId,
        courseId
      }
    })
  }
}

• Depois basta criar o método no controlador:

// src/controllers/favorites-controller.ts

import { Response } from 'express'
import { AuthenticatedRequest } from "../middlewares/auth";
import { favoriteService } from '../services/favoriteService'

export const favoritesController = {

// ...

  },

  // DELETE /favorites/:id
  delete: async (req: AuthenticatedRequest, res: Response) => {
    const userId = req.user!.id
    const courseId = req.params.id

    try {
      await favoriteService.delete(userId, Number(courseId))
      return res.status(204).send()
    } catch (err) {
      if (err instanceof Error) {
        return res.status(400).json({ message: err.message })
      }
    }
  }
}

• E por último criar a rota:

// src/routes.ts

// ...

router.get('/favorites', ensureAuth, favoritesController.index)
router.post('/favorites', ensureAuth, favoritesController.save)
router.delete('/favorites', ensureAuth, favoritesController.delete)

export { router }