Table of Contents

About

This article is about HTTP cookies management in the client side (browser) via javascript.

Cookie are one way to store data in the browser.

document.cookie is a property of the browser document that returns the HTTP cookies that apply to the Document. If no cookies or cookies can't be applied to this resource, the empty string is returned.

With the Web API and Document cookie property

Management

DevTool

You can browse the cookies with the devtool

Cookie Devtool

or an browser extension. Example: Chrome extension Edit this cookie

HttpOnly

A cookie set with the HttpOnly flag, tells the browser that Javascript cannot access this cookie (ie the cookie should only be managed by the server and set in the browser request)

Set

Set two cookies 

document.cookie = "name=nico";
document.cookie = "favorite_color=blue";

Get

All

  • Read the cookies. The cookies are in a string separated with a ;
console.log("All the cookies:");
console.log(document.cookie);
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For the value of the google analytics cookie, see Google Analytics - Utma Cookie

Filter

  • Only the cookie that starts with an underscore
console.log("All the cookies:");
console.log(document.cookie.split("; ").filter( (item) => item.trim().startsWith('_') ));
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by name

There is no function in the Javascript Web API to get a cookie by name.

We need to parse the value of document.cookie. This is a string of all cookies in a key pair format separated by a ;

  • Setting a cookie
cookie_key = "name";
document.cookie = cookie_key+"=nico";
  • Regular expression method. Because the key value is saved in variable, we cannot create a regular expression pattern as a string and need to use a regexp constructor
regexp = new RegExp("(?:(?:^|.*;\\s*)"+cookie_key+"\\s*\\=\\s*([^;]*).*$)|^.*$");
var cookieValue = document.cookie.replace(regexp, "$1");
console.log("Regular expression    : The value of the cookie with the name key is ("+cookieValue+")");

var cookieValue = document.cookie
    .split(";")
    .filter( (item) => item.trim().startsWith(cookie_key) )[0]
    .split("=")[1];
console.log("Functional Programming: The value of the cookie with the name key is ("+cookieValue+")");
  • Result
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Delete

To delete a cookie, just set the expiration date in the past. 

document.cookie = "key=; expires=Thu, 01 Jan 1970 00:00:00 GMT";

Security Consideration

Library

Example: 

import Cookies from "js-cookie";
Cookies.get('cookie-name');