Definition
Fetch Standard defines Headers
[Exposed=(Window,Worker)]
interface Headers {
constructor(optional HeadersInit init);
undefined append(ByteString name, ByteString value);
undefined delete(ByteString name);
ByteString? get(ByteString name);
sequence<ByteString> getSetCookie();
boolean has(ByteString name);
undefined set(ByteString name, ByteString value);
iterable<ByteString, ByteString>;
};