Function mapFactory

src/Operations.js:245–279

(collection, mapper, context)

}

export function mapFactory(collection, mapper, context) {
  const mappedSequence = makeSequence(collection);
  mappedSequence.size = collection.size;
  mappedSequence.has = (key) => collection.has(key);
  mappedSequence.get = (key, notSetValue) => {
    const v = collection.get(key, NOT_SET);
    return v === NOT_SET
      ? notSetValue
      : mapper.call(context, v, key, collection);
  };
  mappedSequence.__iterateUncached = function (fn, reverse) {
    return collection.__iterate(
      (v, k, c) => fn(mapper.call(context, v, k, c), k, this) !== false,
      reverse
    );
  };
  mappedSequence.__iteratorUncached = function (type, reverse) {
    const iterator = collection.__iterator(ITERATE_ENTRIES, reverse);
    return new Iterator(() => {
      const step = iterator.next();
      if (step.done) {
        return step;
      }
      const entry = step.value;
      const key = entry[0];
      return iteratorValue(
        type,
        key,
        mapper.call(context, entry[1], key, collection),
        step
      );
    });
  };
  return mappedSequence;
}

export function reverseFactory(collection, useKeys) {
  const reversedSequence = makeSequence(collection);