lodash/test/isEmpty.spec.ts

import assert from 'node:assert';
import lodashStable from 'lodash';

import {
    empties,
    stubTrue,
    slice,
    symbol,
    args,
    push,
    arrayProto,
    realm,
    MAX_SAFE_INTEGER,
} from './utils';

import isEmpty from '../src/isEmpty';

describe('isEmpty', () => {
    it('should return `true` for empty values', () => {
        const expected = lodashStable.map(empties, stubTrue),
            actual = lodashStable.map(empties, isEmpty);

        assert.deepStrictEqual(actual, expected);

        assert.strictEqual(isEmpty(true), true);
        assert.strictEqual(isEmpty(slice), true);
        assert.strictEqual(isEmpty(1), true);
        assert.strictEqual(isEmpty(NaN), true);
        assert.strictEqual(isEmpty(/x/), true);
        assert.strictEqual(isEmpty(symbol), true);
        assert.strictEqual(isEmpty(), true);

        if (Buffer) {
            assert.strictEqual(isEmpty(new Buffer(0)), true);
            assert.strictEqual(isEmpty(new Buffer(1)), false);
        }
    });

    it('should return `false` for non-empty values', () => {
        assert.strictEqual(isEmpty([0]), false);
        assert.strictEqual(isEmpty({ a: 0 }), false);
        assert.strictEqual(isEmpty('a'), false);
    });

    it('should work with an object that has a `length` property', () => {
        assert.strictEqual(isEmpty({ length: 0 }), false);
    });

    it('should work with `arguments` objects', () => {
        assert.strictEqual(isEmpty(args), false);
    });

    it('should work with prototype objects', () => {
        function Foo() {}
        Foo.prototype = { constructor: Foo };

        assert.strictEqual(isEmpty(Foo.prototype), true);

        Foo.prototype.a = 1;
        assert.strictEqual(isEmpty(Foo.prototype), false);
    });

    it('should work with jQuery/MooTools DOM query collections', () => {
        function Foo(elements) {
            push.apply(this, elements);
        }
        Foo.prototype = { length: 0, splice: arrayProto.splice };

        assert.strictEqual(isEmpty(new Foo([])), true);
    });

    it('should work with maps', () => {
        if (Map) {
            lodashStable.each([new Map(), realm.map], (map) => {
                assert.strictEqual(isEmpty(map), true);
                map.set('a', 1);
                assert.strictEqual(isEmpty(map), false);
                map.clear();
            });
        }
    });

    it('should work with sets', () => {
        if (Set) {
            lodashStable.each([new Set(), realm.set], (set) => {
                assert.strictEqual(isEmpty(set), true);
                set.add(1);
                assert.strictEqual(isEmpty(set), false);
                set.clear();
            });
        }
    });

    it('should not treat objects with negative lengths as array-like', () => {
        function Foo() {}
        Foo.prototype.length = -1;

        assert.strictEqual(isEmpty(new Foo()), true);
    });

    it('should not treat objects with lengths larger than `MAX_SAFE_INTEGER` as array-like', () => {
        function Foo() {}
        Foo.prototype.length = MAX_SAFE_INTEGER + 1;

        assert.strictEqual(isEmpty(new Foo()), true);
    });

    it('should not treat objects with non-number lengths as array-like', () => {
        assert.strictEqual(isEmpty({ length: '0' }), false);
    });

    it('should return an unwrapped value when implicitly chaining', () => {
        assert.strictEqual(_({}).isEmpty(), true);
    });

    it('should return a wrapped value when explicitly chaining', () => {
        assert.ok(_({}).chain().isEmpty() instanceof _);
    });
});