Simple functions for working with browser's cookie. Covered by unit tests on Jest

cookie.js

/**
 * Cookie functions
 * @see https://javascript.info/cookie
 */

/**
 * Returns the cookie with the given name,
 * or undefined if not found
 * @see https://javascript.info/cookie#getcookie-name
 * @param {string} name Cookie name
 * @returns {string} Cookie value
 */
export function getCookie(name) {
    let matches = document.cookie.match(new RegExp(
        '(?:^|; )' + name.replace(/([\.$?*|{}\(\)\[\]\\\/\+^])/g, '\\$1') + '=([^;]*)'
    ));
    return matches ? decodeURIComponent(matches[1]) : undefined;
}

/**
 * Sets the cookie name to the given value with path=/ by default
 * @see https://javascript.info/cookie#setcookie-name-value-options
 * @param {string} name Cookie name
 * @param {string} value Cookie value
 * @param {Object} options Additional params
 */
export function setCookie(name, value, options = {}) {
    options = {
        path: '/',
        ...options
    };

    if (options.hasOwnProperty('expires') && options.expires.hasOwnProperty('toUTCString')) {
        options.expires = options.expires.toUTCString();
    }

    let updatedCookie = encodeURIComponent(name) + '=' + encodeURIComponent(value);

    for (let optionKey in options) {
        updatedCookie += '; ' + optionKey;
        let optionValue = options[optionKey];
        if (optionValue !== true) {
            updatedCookie += '=' + optionValue;
        }
    }

    document.cookie = updatedCookie;
}

/**
 * Deletes the cookie with a given name
 * @param {string} name Cookie name
 */
export function deleteCookie(name) {
    setCookie(name, "", {
        'max-age': -1
    });
}

cookie.test.js

import { getCookie, setCookie, deleteCookie } from './cookie';

describe('getCookie()', () => {
    beforeEach(() => {
        document.cookie = 'existingKey=correctValue';
    });

    afterAll(() => {
        document.cookie = 'existingKey=; path=/; max-age=-1';
    });

    test('should return cookie value if the cookie exists', () => {
        const result = getCookie('existingKey');
        expect(result).toEqual('correctValue');
    });

    test('should return undefined if the cookie does not exist', () => {
        const result = getCookie('failKey');
        expect(result).toEqual(undefined);
	});
});

describe('setCookie()', () => {
    beforeEach(() => {
        document.cookie = 'testKey=; path=/; max-age=-1';
    });

    afterAll(() => {
		document.cookie = 'testKey=; path=/; max-age=-1';
    });

    test('should save the cookie if a key and value are passed', () => {
        setCookie('testKey', 'testValue');
		expect(document.cookie).toEqual('testKey=testValue');
    });
});

describe('deleteCookie()', () => {
    beforeEach(() => {
        document.cookie = 'deletingKey=deletingValue';
    });

    test('first check that cookie exists', () => {
        const result = getCookie('deletingKey');
		expect(result).toEqual('deletingValue');
    });

    test('should delete the cookie', () => {
        deleteCookie('deletingKey');
        const result = getCookie('deletingKey');
		expect(result).toEqual(undefined);
    });
});