declarations.d.ts

interface Body<T> {
  readonly body: ReadableStream<Uint8Array> | null;
  readonly bodyUsed: boolean;
  arrayBuffer(): Promise<ArrayBuffer>;
  blob(): Promise<Blob>;
  formData(): Promise<FormData>;
  json(): Promise<T>;
  text(): Promise<string>;
}

interface Response<T> extends Body<T> {
  readonly headers: Headers;
  readonly ok: boolean;
  readonly redirected: boolean;
  readonly status: number;
  readonly statusText: string;
  readonly type: ResponseType;
  readonly url: string;
  clone(): Response<T>;
}