Request: duplex property

Limited availability

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.

Value

A string with the following possible value:

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

Notes

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.

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"

Specifications

Browser compatibility

See also

• Fetch API
• Request() constructor
• RequestInit.duplex in request options
• Consuming a fetch as a stream