iter-tools-es/impls/async-interleave-ready/async-interleave-ready.js

The iterable toolbox

const {
  asyncIterableCurry
} = require('../../internal/async-iterable.js');

const {
  raceTo
} = require('./internal/race-to.js');

async function* __asyncInterleaveReady(sources) {
  const iterators = sources.map(iterable => iterable[Symbol.asyncIterator]());
  const stepPromises = iterators.map((iter, idx) => iter.next().then(step => ({
    idx,
    step
  })));
  let ready;

  while ((ready = await raceTo(({
    step
  }) => !step.done, null, stepPromises)) !== null) {
    const {
      idx,
      step
    } = ready;
    yield step.value;
    stepPromises[idx] = iterators[idx].next().then(step => ({
      idx,
      step
    }));
  }
}

exports.__asyncInterleaveReady = __asyncInterleaveReady;
const asyncInterleaveReady = /*#__PURE__*/asyncIterableCurry(__asyncInterleaveReady, {
  variadic: true
});
exports.asyncInterleaveReady = asyncInterleaveReady;