fetchMode( request: Request,): null | "same-origin" | "navigate" | "cors" | "no-cors" | "websocket" Returns null | "same-origin" | "navigate" | "cors" | "no-cors" | "websocket"
fetchMode( headers: Headers,): null | "same-origin" | "navigate" | "cors" | "no-cors" | "websocket" Returns null | "same-origin" | "navigate" | "cors" | "no-cors" | "websocket"
See
https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Sec-Fetch-Mode