lodash/test/dropWhile.spec.ts

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

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

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

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

        assert.deepStrictEqual(actual, [3, 4]);
    });

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

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

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

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

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

    it('should work with `_.property` shorthands', () => {
        assert.deepStrictEqual(dropWhile(objects, 'b'), objects.slice(2));
    });

    it('should work in a lazy sequence', () => {
        const array = lodashStable.range(1, LARGE_ARRAY_SIZE + 3),
            predicate = function (n) {
                return n < 3;
            },
            expected = dropWhile(array, predicate),
            wrapped = _(array).dropWhile(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 `drop`', () => {
        const array = lodashStable.range(1, LARGE_ARRAY_SIZE + 3);

        const actual = _(array)
            .dropWhile((n) => n === 1)
            .drop()
            .dropWhile((n) => n === 3)
            .value();

        assert.deepEqual(actual, array.slice(3));
    });
});