Question about handling errors/ return data eg within an express-api

JavaScript
1

Hi,
I have a general question about handling errors/ return data eg within an express-api.
It’s related to the projects from: Information Security And Quality Assurance Certification

I’ll try to explain it with some examples from a book-API:

  1. GET /api/books/5d9c27f93fcfa11b2afb4273
    If I provide a valid id and the entry exists I get a JSON-object like
{
"title": "foo",
"_id": "5d9c27f93fcfa11b2afb4273"
}

=> no error

  1. GET /api/books/999c27f93fcfa11b2afb4299
    The id is valid but there is no result. It is not an error.
    What do I return? An empty object?
    {}

  2. GET /api/books/xxx
    The id is not valid. This is an error.
    What do I return?
    I tried: sending status code 500 in combination with a status text: “id is not valid”

Why? On the frontend jQuery handles errors like this

$.ajax({
  url:'/api/books...',
  type: 'get',
  success: function(data) {...},
  error: function(jqXHR, textStatus, errorThrown ) {
      // use: jqXHR.responseText;
    }
  }

So I have a clear way to handle errors.

My question: Is there a common way to structure the return values in APIs?

In the project-examples it is mixed up: sometimes JSON-objects are returned,
sometimes just text (eg: “all books deleted successfully”), sometimes arrays.

I find it difficult/unhandy If you must always check the type of return data.

At least there should be a common way for handling errors for all requests of an API.

2

Now I found this module:
https://github.com/aofleejay/express-response-formatter

It uses a response that seems to be well organized:

{
 meta: ...
 data: ...
 error: ...
}

But I have not yet tested it.