Cleanest way to handle custom errors with fetch & ES6 promise

Question

I am trying to intelligently handle the success/error responses from our API using fetch & ES6 promises.

Here is how I need to handle response statuses:

Answer 1

I think you can write it out pretty easily:

fetch(…).then(response => {
    if (response.ok)
        return response[response.status == 204 ? "text" : "json"]();
    if (response.status == 422)
        return response.json().then(err => { throw err; });
    if (response.status == 406)
        var error = new AuthentificationError(response.statusText); // or whatever
    else
        var error = new Error(response.statusText)
    error.response = response
    throw error;
})