use-iterator

React hooks collection for JavaScript's Iterator/generator.

• Examples

useForAwaitOf(asyncIterable, deps)

Subscribes to the asyncIterable specified in the argument and as soon as a promise is resolved, immediately starts to await the next promise.

This is similar to for-await-of syntax of JavaScript, but the results are wrapped in React APIs so components will be updated whenever the result changes.

import { on } from 'events-to-async';

const changeEvent = on((handler) => {
  const elm = document.getElementById('text_field');
  elm?.addEventListener('change', handler);
  return () => elm?.removeEventListener('change', handler);
});

const App = () => {
  // subscribe to the change events from #text_field
  const result = useForAwaitOf(changeEvent);

  // latest change event from #text_field
  return <span>{result.value}</span>;
};

Note that this example uses an additional module events-to-async to convert Event objects into AsyncIterator.

useGenerator(generator, deps)

Wraps generator function into a React state. You can call next() to retrieve the next value, and read the latest value from the iterator via value.

const App = () => {
  const result =
    useGenerator <
    string >
    (function* () {
      yield "Let's get started";
      yield 'Choose your username';
      yield 'Upload the avatar';
    },
    []);

  if (result.done) {
    return <div>Tutorial completed!</div>;
  }

  return (
    <div>
      <h2>{result.value}</h2>

      <button onClick={() => result.next()}>Next</button>
    </div>
  );
};

useAsyncGenerator(generator, deps)

Wraps async generator function into a React state. You can call next() to retrieve the next value, and read the latest value from the iterator via value.

This is similar to useGenerator described above, but with async you can return Promises from the generator. This would be useful for sequential network requests such as Web APIs with pagination.

const App = () => {
  const result = useAsyncGenerator<string>(function* () {
    yield fetch('https://example.com?page=1');
    yield fetch('https://example.com?page=2');
    yield fetch('https://example.com?page=3');
  }, []);

  if (result.loading) {
    return <span>Loading...</span>
  }

  return (
    <div>
      <ul>
        {result.value.map((item) => (
          <li>...</li>
        ))}
      </ul>

      <button onClick={()) => result.next()}>
        Next
      </button>
    </div>
  );
};

useIterable(iterable, deps)

Wraps iterable into a React state. You can call next() to retrieve the next value, and read the latest value from the iterator via value.

Argument can be any object that implements [Symbol.iterator] protocol such as String and Array.

const result = useIterable('abcd');

result.next();
result.value === 'a';

result.next();
result.value === 'b';

useAsyncIterable(asyncIterable, deps)

Wraps async iterable into a React state. You can call next() to retrieve the next value, and read the latest value from the iterator via value.

Argument can be any object that implements [Symbol.asyncIterator] protocol.

const result = useAsyncIterable({
  [Symbol.asyncIterator]() {
    return {
      i: 0,
      next() {
        if (this.i < 3) {
          return Promise.resolve({ value: this.i++, done: false });
        }

        return Promise.resolve({ done: true });
      },
    };
  },
});

result.next();
result.loading; // === true while loading
result.value === 1;

useIterator(iterator, deps)

A low-level hook for useIterable and useGenerator. Accepts iterator object and returns a reactive state and a dispatcher.

const result = useIterator({
  next: () {...},
  return: () {...},
  throw: () {...},
});

useAsyncIterator(asyncIterator, deps)

A low-level hook for useAsyncIterable and useAsyncGenerator. Accepts async iterator object and returns a reactive state and a dispatcher.

const result = useAsyncIterator({
  next: () {...},
  return: () {...},
  throw: () {...},
});