Parses a `Cookie` HTTP header value or `document.cookie` into an object

#parseCookie.ts

function decode(str: string) {
  try {
    return decodeURIComponent(str);
  } catch {
    return str;
  }
}

/**
 * Parses a `Cookie` HTTP header value or `document.cookie` into an object.
 *
 * Implementation adapted from https://gist.github.com/rendro/525bbbf85e84fa9042c2?permalink_comment_id=3084097#gistcomment-3084097
 */
export function parseCookie(cookies: string) {
  const obj = Object.create(null) as Record<string, string | undefined>;

  const list = cookies.split(';');

  for (const cookie of list) {
    if (cookie === '') continue;

    const eq = cookie.indexOf('=');

    const key = (eq > 0 ? cookie.slice(0, eq) : cookie).trim();
    const value = eq > 0 ? decode(cookie.slice(eq + 1).trim()) : undefined;

    if (!(key in obj)) {
      obj[key] = value;
    }
  }

  return obj;
}

parseCookie.bench.ts

import { bench, describe } from 'vitest';

import { parseCookie } from './parseCookie';

// Benchs taken from https://github.com/jshttp/cookie/blob/v1.0.2/src/parse.bench.ts

const topSites = {
  'accounts.google.com': '__Aaaa-AAAA=0:0AaaAaaaAAA0aA0aAA0aaAaAAaaaAA:AAAaAA0AAAaAAa0a',
  'amazon.com':
    'aaaaaaa-aa=000-0000000-0000000; bbbbbbb-bb-bbbb=1111111111b; c22c-ccccc=CCC; dddd=dddddd',
  'apple.com': 'aaa=AA',
  'cloudflare.com':
    '__aa_aa=aaA0aaAAaAaaaa0aaaaAAAA_0aa0a.0AAA000aAA0aa-0000000000-0.0.0.0-Aaa00aA0aaAaAA0AaaAAAA0AaAaaaAAA.AaAaAaAA_0aAaAaaAA0AAAAaaAaaaaA0aaAAAaAAAaaaaa0AAa0AAAAAaaA0aaA0a0aaaaaAAA',
  'docs.google.com': '__Aaaa-AAAA=0:aAAaA00AA0A0AAaAAAaAAAAAaA_AAA:aAAA00AAaaAAaaAA',
  'drive.google.com': '__Aaaa-AAAA=0:AA0a0AAaaAaaA0A-AAAA0aaA_0A-aa:0aaAa0aA0aaAAAAa',
  'en.wikipedia.org':
    'AAA-Aaaa-Aaaaaa=00-Aaa-0000; BBB-Bbbb-Bbbbbb-Bbbbbb=11-Bbb-1111; CCC-CC=222; DddDD=DD:DD:Ddd_Ddddddddd:33.33:-333.33:d3; EeeeeeeEeeeeEeeee=4.444',
  'istockphoto.com':
    'aaaaaaa=aAAAAAAaAAAaaa0aa0aAAAa0aAaaaAAA0A%22aaA0aAaaAaa0AAaaaaAAaAaaa0AaaaA%2200a0a00AA00A0aAaAaA0aa%22AAaaAA0000aAa00%220AaAaAAA0AaaAaAAAaaaAaAAa00AaAa0AaaaAaAaAaaaaaaa%22aAaaaAaaAaaaAAAAaAAaaAAaAaaAaaaAAa0A%22--aaA0aaAAAAAaaAAa--a0a%22A%22aAAaAAAa%22AaaAaAA%22%22; bbb=bb=1&bb=1111-11-11B11%2211%2211B; ccc=ccc=22222ccc-2c22-2c22-2222-22c2222c2222; ddd=d=DD%22dDddddDdddD3ddDddd33dddD3dDD33dDd3DDdDdddDdD33D3Dd33DDdd3dDd3dDDdDDDdD3dD3d3D3dDDdd3dddD%223DDDDdd3dD3ddd3dddDdDdD33D3DdDDd3dD3dDddDDdDdDDDdDDDDDDdddDdDdDdD3dddDDDd3DDD3D%22%2233d%22D3DDDDdDDDDDddddDDDdd3DdDDdDDDDdDdddd3ddD3D3DDddd3ddD3D3DDddDddDDDd3DDDDDdD3DDddDdDdDDD3DDDdDDddDDDdDDD3DD33DDddDDD3DDDdDDDdDDD3DDdD%223%223%223&d; eeee=e=eEEEeEee44eE4eeEEeeEEEeEE4444eeE4eE4eEE4%224e%22',
  'maps.google.com':
    'AAA=000=aaaaAa0Aaa0aaaaaaaaaaAAAAAAaaaaAAA0AaAAA0aaaA00AAA0aAAAA0aaA0aAAAAaAAA0aAAAAaaAAaa_AAAAAaA0a0aaaAaaaaa--aa0aAAA0A0AaAA0AAaaAAa0AaAAa0A_aAAAAaAA_aAaAa0AaA0aAa0Aa-AAa0aaaAAaAA-AaaaA0aaAaAA0aaaa',
  'play.google.com':
    'AAA=000=A0AaA-aaaA00AaAAa00A0aaAAaA0AaAaaaa0A_Aa0_AaaAAAaAaa0aa0a-0aAaA0__AaAAaaaaAAaaaaaAAaaa0aAAAa0a_a0aaAAAAAaAaa0aaaaaAaaaaAAA_aAa0aaa0aaa00aaAAAaA0AAAAa00A0A0AaAaA0AAA0A0AAaAA0aaAAa',
  'policies.google.com':
    'AAA=000=AaAAAA_aAAa0aAaaaaAAa000A0AAaAaAAaAaaAa00-0aAaaAAaaAAAA0a0aaA0AaAaaaaaaaaAAAA0a0AAa_AaaAaaaAa_aaAAAaa00aAAAAAA_AAAAa0aA0a0AaA_00A0-0AaA-A_AAaA00aaAAAAAAaAaAaaaa0aaAAa0AaaA0aaAaaa',
  'pt.wikipedia.org':
    'AAA-Aaaa-Aaaaaa=00-Aaa-0000; BBB-Bbbb-Bbbbbb-Bbbbbb=11-Bbb-1111; CccCC=CC:CC:Ccc_Ccccccccc:22.22:-222.22:c2; DddddddDddddDdddd=3.333',
  'sites.google.com': '__Aaaa-AAAA=0:aaaAaAAA0aAAaAAAaAaaAaa0A00AAA:aAAaaaAA_aa0A0aA',
  'support.google.com':
    'AAA=000=aaAAAaaAaaaAaA0aAA-00-AAaA0Aa0A0aaaAaaAa00_aAAAAAaaA0AAa0AAA0aAaA0aA0A0AAAAA0A0aaAAAA0aa-AAaAa00a0AaaaAaaAaa0Aaa0AA0aAAaaaaaAAAaAAAA0AA0AAaaaAa0aAAAaaaaaaAAA_0aaAaaAA0AaA0a0a0aAaA; BBB=111=bbBBBbbBbbbBbB1bBB-11-BBbB1Bb1B1bbbBbbBb11_bBBBBBbbB1BBb1BBB1bBbB1bB1B1BBBBB1B1bbBBBB1bb-BBbBb11b1BbbbBbbBbb1Bbb1BB1bBBbbbbbBBBbBBBB1BB1BBbbbBb1bBBBbbbbbbBBB_1bbBbbBB1BbB1b1b1bBbB',
  't.me': 'aaaa_aaaa=aa0a00a00a000000a0_0000000000000000000',
  'vk.com':
    'aaaaaaa=AAAAAAA; bbbbbbbbb=1; cccccccccc=2222222222222222222_CcCCccCCccc2CcCcCCCccCCCCccc2CccCC2cc2CcCCc; ddddddd=DDDDDDD; eeeeeEEEE=EEEEEEE; fffffffff=5555555555_fFfFffFfffFF55FF5ffffF5ffFFfff5f5F55FfF5fFF; ggggggg=-6%22-6%22-6%226666666666; hhhhhhh=7; iiiiiii=-8%22-8%22-8%228888888888',
  'www.google.com':
    'AAA=AAAA0aaA00aaAaA-aaA0AaAaaAaa0aaAaAaaAAaA0AA00A0aAaAAAA0aaA; BBB=111=bbb111bBBb11-bbbBbbBBb11BbBB1bbb-bbBbbBBBbb-bbbb1BBbBBbbbb_bBb1BbbBBB1B1bBbb1b11bbBB11B11BBbBbbBB11BBBbb1b-BBbBBbBbBBB11bBbBB1BbbBBBBbbBbbBBbbB1b1bBb1B_BBb1BBB1bB1BbBBBbb1bB11b1bbbBBbbBbBBBbbbBBBb',
  'youtu.be':
    'AAA=0; BBB=bbbBbBbbbbb; CCCCCCC_CCCC2_CCCC=Cccc-cCCcCC; DDDDDDD_DDDDDDD_DDDDDDDD=DdDDDdDDDdDdDD%22%22',
  'youtube.com':
    'AAA=0; BBB=BbBbbbb1bBb; CCCCCCC_CCCC2_CCCC=CCc2ccCccCc; DDDDDDD_DDDDDDD_DDDDDDDD=DdDDDdDDDdDdDd%22%22',
  'example.com': ''
};

function genCookies(count: number) {
  let str = '';
  for (let i = 0; i < count; i++) {
    str += `; foo${i}=bar`;
  }
  return str.slice(2);
}

bench('simple', () => {
  parseCookie('foo=bar');
});

bench('decode', () => {
  parseCookie('foo=hello%20there!');
});

bench('unquote', () => {
  parseCookie('foo="foo bar"');
});

const duplicates = `${genCookies(2)}; ${genCookies(2)}`;
bench('duplicates', () => {
  parseCookie(duplicates);
});

const cookies10 = genCookies(10);
bench('10 cookies', () => {
  parseCookie(cookies10);
});

const cookies100 = genCookies(100);
bench('100 cookies', () => {
  parseCookie(cookies100);
});

describe('parse top-sites', () => {
  Object.entries(topSites).forEach(([domain, value]) => {
    bench(`parse ${domain}`, () => {
      parseCookie(value);
    });
  });
});

parseCookie.test.ts

import { expect, it } from 'vitest';

import { parseCookie } from './parseCookie';

// Tests taken from https://github.com/jshttp/cookie/blob/v1.0.2/src/parse.spec.ts

it('should parse cookie string to object', () => {
  expect(parseCookie('foo=bar')).toEqual({ foo: 'bar' });
  expect(parseCookie('foo=123')).toEqual({ foo: '123' });
});

it('should ignore optional whitespaces (OWS)', () => {
  expect(parseCookie('FOO    = bar;   baz  =   raz')).toEqual({
    FOO: 'bar',
    baz: 'raz'
  });
});

it('should parse cookie with empty value', () => {
  expect(parseCookie('foo=; bar=')).toEqual({ foo: '', bar: '' });
});

it('should parse cookie with minimum length', () => {
  expect(parseCookie('f=')).toEqual({ f: '' });
  expect(parseCookie('f=;b=')).toEqual({ f: '', b: '' });
});

it('should URL-decode values', () => {
  expect(parseCookie('foo="bar=123456789&name=Magic+Mouse"')).toEqual({
    foo: '"bar=123456789&name=Magic+Mouse"'
  });

  expect(parseCookie('email=%20%22%2c%3b%2f')).toEqual({ email: ' ",;/' });
});

it('should trim whitespace around key and value', () => {
  expect(parseCookie('  foo  =  "bar"  ')).toEqual({ foo: '"bar"' });
  expect(parseCookie('  foo  =  bar  ;  fizz  =  buzz  ')).toEqual({
    foo: 'bar',
    fizz: 'buzz'
  });
  expect(parseCookie(' foo = " a b c " ')).toEqual({ foo: '" a b c "' });
  expect(parseCookie(' = bar ')).toEqual({ '': 'bar' });
  expect(parseCookie(' foo = ')).toEqual({ foo: '' });
  expect(parseCookie('   =   ')).toEqual({ '': '' });
  expect(parseCookie('\tfoo\t=\tbar\t')).toEqual({ foo: 'bar' });
});

it('should return original value on escape error', () => {
  expect(parseCookie('foo=%1;bar=bar')).toEqual({ foo: '%1', bar: 'bar' });
});

it('should ignore cookies without value', () => {
  expect(parseCookie('foo=bar;fizz  ;  buzz')).toEqual({ foo: 'bar' });
  expect(parseCookie('  fizz; foo=  bar')).toEqual({ foo: 'bar' });
});

it('should ignore duplicate cookies', () => {
  expect(parseCookie('foo=%1;bar=bar;foo=boo')).toEqual({
    foo: '%1',
    bar: 'bar'
  });
  expect(parseCookie('foo=false;bar=bar;foo=true')).toEqual({
    foo: 'false',
    bar: 'bar'
  });
  expect(parseCookie('foo=;bar=bar;foo=boo')).toEqual({
    foo: '',
    bar: 'bar'
  });
});

it('should parse native properties', () => {
  expect(parseCookie('toString=foo;valueOf=bar')).toEqual({
    toString: 'foo',
    valueOf: 'bar'
  });
});