Async iterator for pagination

main.js

class Token {
  nextRange() {
    return `${this._range}-`;
  }

  feed(response) {
    this._range = response.headers.Range;
  }
}

class Request {
  constructor(input) {
    this._input = input;
  }
  
  paginationToken() {
    return new Token();
  }

  do(token) {
    return {
      async next() {
        const raw = await fetch(this._input, {
          headers: {
            'Content-Range': token.nextRange(),
          }
        });
        return new Response(raw);
      },
      [Symbol.asyncIterator]() {
        return this;
      }
    }
  }
}

const request = new Request();
const token = request.paginationToken();
for await (const response of request.do(token)) {
  // consume response.body
  token.feed(response);
}