iterable-iterator/slice

import {iter} from '@iterable-iterator/iter';

/**
 * Same as
 * <code>map( [ i , x ] => x , filter( [ i , x ] => (new Set( range( start ,
 * stop , step ) ) ).has( i ) , enumerate( iterable ) ) );</code>.
 *
 * @param {Iterable} iterable - The input iterable.
 * @param {Number} start - Where to start the slice.
 * @param {Number} stop - Where to stop the slice.
 * @param {Number} step - The step of the slice.
 * @returns {IterableIterator}
 */
export default function* slice(iterable, start, stop, step) {
    const iterator = iter(iterable);

    while (start > 0) {
        if (iterator.next().done) {
            return;
        }

        --start;
        --stop;
    }

    while (stop > 0) {
        const current = iterator.next();

        if (current.done) {
            return;
        }

        yield current.value;

        --stop;

        let n = step;

        while (n > 1) {
            if (iterator.next().done) {
                return;
            }

            --n;
        }
    }
}