multiplex/multiplex.js

import Iterable from '../iteration/iterable';
import Iterator from '../iteration/iterator';
import buffer from '../utils/buffer';
import asArray from '../utils/as-array';
import assertType from '../utils/assert-type';
import assertNotNull from '../utils/assert-not-null';
import $iterator from '../iteration/iterator-factory';

export default function skipIterator(source, count) {
    assertNotNull(source);
    assertType(count, Number);
    count = Math.max(count, 0);

    var arr = asArray(source);

    if (arr !== null) {
        return new Iterable(buffer(arr).slice(count));
    }

    return new Iterable(function () {
        var it = $iterator(source),
            next;

        return new Iterator(function () {
            while (count > 0 && !it.next().done) {
                count--;
            }
            if (count <= 0) {
                while (!(next = it.next()).done) {
                    return {
                        value: next.value,
                        done: false
                    };
                }
            }
            return {
                done: true
            };
        });
    });
}