Note: This feature is available in Web Workers.
The body read-only property of the Request interface contains a ReadableStream with the body contents that have been added to the request. Note that a request using the GET or HEAD method cannot have a body and null is returned in these cases.
A ReadableStream or null.
const request = new Request("/myEndpoint", {
method: "POST",
body: "Hello world",
});
request.body; // ReadableStream