ReadableStreamDefaultReader
interface ReadableStreamDefaultReader <R = any> {
readonly closed: Promise<void>;
cancel(reason?: any): Promise<void>;
read(): Promise<ReadableStreamReadResult<R>>;
releaseLock(): void;
}var ReadableStreamDefaultReader: {
prototype: ReadableStreamDefaultReader;
new <R>(stream: ReadableStream<R>): ReadableStreamDefaultReader<R>;
};