How to use instanceof in a switch statement

A good option is to use the constructor property of the object:

// on reject / failure
switch (error.constructor) {
    case NotAllowedError:
        return res.send(400);
    case DatabaseEntryNotFoundError:
        return res.send(404);
    default:
        log('Failed to do something async with an unspecified error: ', error);
        return res.send(500);
}

Notice that the constructor must match exactly with the one that object was created (suppose error is an instance of NotAllowedError and NotAllowedError is a subclass of Error):

• error.constructor === NotAllowedError is true
• error.constructor === Error is false

This makes a difference from instanceof, which can match also the super class:

• error instanceof NotAllowedError is true
• error instanceof Error is true

Check this interesting post about constructor property.