CODEWITHSUNDEEP
javascripthttpfetch-api
Jacob
Jacob

Reputation: 78850

Ignoring body in a JavaScript fetch response

I have some code that wants to issue a request and check whether the request is successful, but it does not care about the response body:

async function doTheThing() {
  const response = await fetch(someUrl, { method: 'POST' });
  if (!response.ok) {
    throw new Error(`Request failed with status ${response.status}`);
  }
}

As I understand it, the response body is not downloaded yet at this point. If we leave it hanging and don't follow up with something like:

const body = await response.json();

...will the request/response remain open and waiting until perhaps GC occurs? If so, is there a way to cleanly ignore the rest of the response stream without causing issues?

Upvotes: 2

Views: 2747

Answers (2)

PGT
PGT

Reputation: 2019

You can just do a HEAD if it doesn't have to be a POST and you just want to check if you'll receive a 400 or 500 series error

https://developers.google.com/web/ilt/pwa/working-with-the-fetch-api#example_head_requests

Example: HEAD requests By default fetch uses the GET method, which retrieves a specific resource, but other request HTTP methods can also be used.

HEAD requests are just like GET requests except the body of the response is empty. You can use this kind of request when all you want the file's metadata, and you want or need the file's data to be transported.

If you are stuck with a POST request, it's controlled on server-side and you will receive whatever the server returns, there's no web standard that dictates you can tell the server to not send anything, so the server would have to be explicitly written to allow this behaviour.

If you do not care, the GC will run its course once you've exited this particular scope and response is no longer needed. You do not need to await it or anything but it will download in the background (held in memory) and then thrown away when GC runs.

Upvotes: 1

rh16
rh16

Reputation: 1073

will the request/response remain open and waiting until perhaps GC occurs?

In short, no.

const body = await response.json();

instructs your code to wait until the response body is downloaded, it does not trigger the body download. Unless there is a reason not to, the response body stream will download the content and then close.

You can read about the process in the fetch spec.

It is possible to abort a fetch request after it has been started, but this is not recommended due to issues with browser support. See How do I cancel an HTTP fetch() request?

Upvotes: 1

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