Accessing body of error response

[sarahannali]

I'm currently trying to make my post request handle a specific error message. The response body of the error message is fine through postman, but the output of the error to the console is:

data: Response
  body: ReadableStream
  bodyUsed: true
  headers: Headers {}
  ok: false
  redirected: false
  status: 400
  statusText: ""
  type: "basic"
  url: "https://localhost:3003/api/type"
message: "Failed to fetch: 400 "
status: 400

which is the correct response, but the body is a readable stream. I can access the body by reading this stream, but it's clunky. I'd like to be able to just output my error.data.body.

Perhaps I'm just running my request wrong. Here's how it's formatted:

const addType = useAddType({}); // generated post function for API named AddType that takes in a name

  addType
      .mutate({
          name: "testName"
      })
      .then(res => {
          console.log(res);
      })
      .catch(err => {
          console.log(err); // contains a body with a more detailed error message
      })

This request works fine, I just can't access the body of the error.