lodash/test/zipWith.spec.js

import lodashStable from 'lodash';
import { slice } from './utils';
import zipWith from '../src/zipWith';
import zip from '../src/zip';

describe('zipWith', () => {
    it('should zip arrays combining grouped elements with `iteratee`', () => {
        const array1 = [1, 2, 3];
        const array2 = [4, 5, 6];
        const array3 = [7, 8, 9];

        let actual = zipWith(array1, array2, array3, (a, b, c) => a + b + c);
        expect(actual).toEqual([12, 15, 18]);

        actual = zipWith(array1, [], (a, b) => a + (b || 0));
        expect(actual).toEqual([1, 2, 3]);
    });

    it('should provide correct `iteratee` arguments', () => {
        let args;

        zipWith([1, 2], [3, 4], [5, 6], function () {
            args || (args = slice.call(arguments));
        });

        expect(args).toEqual([1, 3, 5]);
    });

    it('should perform a basic zip when `iteratee` is nullish', () => {
        const array1 = [1, 2];
        const array2 = [3, 4];
        const values = [, null, undefined];
        const expected = lodashStable.map(values, lodashStable.constant(zip(array1, array2)));

        const actual = lodashStable.map(values, (value, index) =>
            index ? zipWith(array1, array2, value) : zipWith(array1, array2),
        );

        expect(actual).toEqual(expected);
    });
});