lodash/test/bindKey.spec.ts

import assert from 'node:assert';
import { slice } from './utils';
import bindKey from '../src/bindKey';

describe('bindKey', () => {
    it('should work when the target function is overwritten', () => {
        const object = {
            user: 'fred',
            greet: function (greeting) {
                return `${this.user} says: ${greeting}`;
            },
        };

        const bound = bindKey(object, 'greet', 'hi');
        assert.strictEqual(bound(), 'fred says: hi');

        object.greet = function (greeting) {
            return `${this.user} says: ${greeting}!`;
        };

        assert.strictEqual(bound(), 'fred says: hi!');
    });

    it('should support placeholders', () => {
        const object = {
            fn: function () {
                return slice.call(arguments);
            },
        };

        const ph = bindKey.placeholder,
            bound = bindKey(object, 'fn', ph, 'b', ph);

        assert.deepStrictEqual(bound('a', 'c'), ['a', 'b', 'c']);
        assert.deepStrictEqual(bound('a'), ['a', 'b', undefined]);
        assert.deepStrictEqual(bound('a', 'c', 'd'), ['a', 'b', 'c', 'd']);
        assert.deepStrictEqual(bound(), [undefined, 'b', undefined]);
    });

    it('should use `_.placeholder` when set', () => {
        const object = {
            fn: function () {
                return slice.call(arguments);
            },
        };

        const _ph = (_.placeholder = {}),
            ph = bindKey.placeholder,
            bound = bindKey(object, 'fn', _ph, 'b', ph);

        assert.deepEqual(bound('a', 'c'), ['a', 'b', ph, 'c']);
        delete _.placeholder;
    });

    it('should ensure `new bound` is an instance of `object[key]`', () => {
        function Foo(value) {
            return value && object;
        }

        var object = { Foo: Foo },
            bound = bindKey(object, 'Foo');

        assert.ok(new bound() instanceof Foo);
        assert.strictEqual(new bound(true), object);
    });
});