lodash/test/takeWhile.spec.ts

import assert from 'node:assert';
import lodashStable from 'lodash';
import { slice, LARGE_ARRAY_SIZE, square } from './utils';
import takeWhile from '../src/takeWhile';

describe('takeWhile', () => {
    const array = [1, 2, 3, 4];

    const objects = [
        { a: 2, b: 2 },
        { a: 1, b: 1 },
        { a: 0, b: 0 },
    ];

    it('should take elements while `predicate` returns truthy', () => {
        const actual = takeWhile(array, (n) => n < 3);

        assert.deepStrictEqual(actual, [1, 2]);
    });

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

        takeWhile(array, function () {
            args = slice.call(arguments);
        });

        assert.deepStrictEqual(args, [1, 0, array]);
    });

    it('should work with `_.matches` shorthands', () => {
        assert.deepStrictEqual(takeWhile(objects, { b: 2 }), objects.slice(0, 1));
    });

    it('should work with `_.matchesProperty` shorthands', () => {
        assert.deepStrictEqual(takeWhile(objects, ['b', 2]), objects.slice(0, 1));
    });
    it('should work with `_.property` shorthands', () => {
        assert.deepStrictEqual(takeWhile(objects, 'b'), objects.slice(0, 2));
    });

    it('should work in a lazy sequence', () => {
        const array = lodashStable.range(LARGE_ARRAY_SIZE),
            predicate = function (n) {
                return n < 3;
            },
            expected = takeWhile(array, predicate),
            wrapped = _(array).takeWhile(predicate);

        assert.deepEqual(wrapped.value(), expected);
        assert.deepEqual(wrapped.reverse().value(), expected.slice().reverse());
        assert.strictEqual(wrapped.last(), _.last(expected));
    });

    it('should work in a lazy sequence with `take`', () => {
        const array = lodashStable.range(LARGE_ARRAY_SIZE);

        const actual = _(array)
            .takeWhile((n) => n < 4)
            .take(2)
            .takeWhile((n) => n === 0)
            .value();

        assert.deepEqual(actual, [0]);
    });

    it('should provide correct `predicate` arguments in a lazy sequence', () => {
        let args,
            array = lodashStable.range(LARGE_ARRAY_SIZE + 1),
            expected = [1, 0, lodashStable.map(array.slice(1), square)];

        _(array)
            .slice(1)
            .takeWhile(function (value, index, array) {
                args = slice.call(arguments);
            })
            .value();

        assert.deepEqual(args, [1, 0, array.slice(1)]);

        _(array)
            .slice(1)
            .map(square)
            .takeWhile(function (value, index, array) {
                args = slice.call(arguments);
            })
            .value();

        assert.deepEqual(args, expected);

        _(array)
            .slice(1)
            .map(square)
            .takeWhile(function (value, index) {
                args = slice.call(arguments);
            })
            .value();

        assert.deepEqual(args, expected);

        _(array)
            .slice(1)
            .map(square)
            .takeWhile(function (value) {
                args = slice.call(arguments);
            })
            .value();

        assert.deepEqual(args, [1]);

        _(array)
            .slice(1)
            .map(square)
            .takeWhile(function () {
                args = slice.call(arguments);
            })
            .value();

        assert.deepEqual(args, expected);
    });
});