src/enumerate.js

import {_count} from '@iterable-iterator/count';
import _zip2 from './_zip2.js';

/**
 * Yields (index,element) tuples where the elements are taken from the input
 * iterable. You can choose the starting index. The starting index is
 * <code>0</code> by default.
 *
 * @example
 * // returns [ [ 0 , 'a' ] , [ 1 , 'b' ] , [ 2 , 'c' ] ]
 * list( enumerate( 'abc' ) ) ;
 *
 * @example
 * // returns [ [ 1 , 'a' ] , [ 2 , 'b' ] , [ 3 , 'c' ] ]
 * list( enumerate( 'abc' , 1 ) ) ;
 *
 * @param {Iterable} iterable - The input iterable.
 * @param {number} [start=0] - The starting index.
 * @returns {IterableIterator}
 */
export default function enumerate(iterable, start = 0) {
	return _zip2(_count(start, 1), iterable);
}