CODEWITHSUNDEEP
typescriptfetch-api
Marian Tarlungeanu
Marian Tarlungeanu

Reputation: 313

Why a "Failed to execute 'json' on 'Response'" error is raised after destructuring the response object

I'm implementing my own fetch method that uses the fetch API. While doing this I've encountered a raised error that I cannot explain.

The code fragment looks like this:

    const response: Response = await fetch(url, options);
    const { json } = response;

    return json();

The problem is that this code triggers a promise rejection:

TypeError: Failed to execute 'json' on 'Response': body stream is locked

I know that the json method can only be called once, which it does.
The fetch itself doesn't fail. If I return directly response.json(), no rejection arises.

My question is why using the destructuring assignment on the response object, locks the body of the response which is a ReadableStream.

Upvotes: 3

Views: 2278

Answers (1)

Marian Tarlungeanu
Marian Tarlungeanu

Reputation: 313

The reason this happens is that destructuring the object results in decoupling the json method from the original scope of the response.

One solution would be:

    const response: Response = await fetch(url, options);
    const { json } = response;

    return json.bind(response)();

Upvotes: 2

Related Questions