Request: duplex property

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

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Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The duplex read-only property of the Request interface returns the duplex mode of the request, which determines whether the browser must send the entire request before processing the response.

Although duplex can be passed as an option when constructing a Request, it is not currently exposed as a readable property on the resulting Request object in all browsers.

Value

A string with the following possible value:

"half": The browser must send the entire request before processing the response.

Examples

Checking a request's duplex mode

const stream = new ReadableStream({/* ... */});
const request = new Request("/upload", {
  method: "POST",
  body: stream,
  duplex: "half", // Required for streaming requests
});

console.log(request.duplex); // "half"