javascript fetch returns a stream and content wrapped in a callback

Question

Looking for the best way to access the data returned from an api call. The string looks like this:

'https://somedomain/data.json?callback=someCallback'

and I fetch like this:

fetch('https://somedomain/data.json?callback=someCallback')
.then(response => response.text())
.then(text => console.log(text));

and this will give me the data that I need but it wrapped up in the callback like so:

someCallback({/* json like data here */})

I know the returned data is a stream because if I do soemthing like this:

.then(response => {
     const reader = response.body.getReader();
     console.log(reader);
});

I get back this:

ReadableStreamDefaultReader {closed: Promise}

Ideally I would like this data in the form of a json object so how would I go about getting that. Or if that is just bad practice how to read this?