Store data in cookies using JavaScript

Cookies are small data files that are stored on a user’s device when they browse the internet. They are commonly used to store user preferences, login credentials, and other small pieces of information. In JavaScript, cookies can be created, read, and deleted using the document.cookie object. In this article, we will explore how to store data in a cookie using JavaScript and provide multiple examples to illustrate the concept.

Creating a Cookie

Creating a cookie in JavaScript involves setting the document.cookie property to a string that contains the data to be stored, along with any optional parameters. The basic syntax for creating a cookie is as follows:

document.cookie = "key=value; expires=expiration_time; path=path_name";

Here, key is the name of the cookie, and value is the data to be stored. The expires parameter sets the expiration date for the cookie. After this date, the cookie will no longer be stored on the user’s device. The path parameter sets the path for which the cookie is valid. This is useful for limiting the scope of the cookie to specific parts of a website.

Let’s say we want to create a cookie that stores a user’s name and expires after 24 hours. We can do this using the following code:

const name = "John";
const expires = new Date(Date.now() + 86400e3).toUTCString(); // 24 hours from now
document.cookie = `name=${name}; expires=${expires}; path=/`;

This code creates a cookie with the name name and the value John, which will expire after 24 hours. The path parameter is set to /, which means the cookie will be valid for the entire website.

Examples

Here are some additional examples to demonstrate how to store data in a cookie using JavaScript.

Example 1: Storing a single value in a cookie

Suppose we want to store a user’s preferred language in a cookie. Here’s how we can do it:

function setLanguageCookie(lang) {
  document.cookie = `lang=${lang};path=/`;
}

In the above code, we define a function setLanguageCookie that takes a lang parameter (the language code) and sets a cookie with the name lang and value equal to lang. We also specify the path attribute as / to ensure that the cookie is accessible from any page on the website.

Example 2: Storing multiple values in a cookie

Sometimes we may need to store multiple values in a cookie. We can achieve this by serializing the data into a string (using JSON.stringify) and storing it in the cookie.

function setUserInfoCookie(name, email, age) {
  const userInfo = { name, email, age };
  const userInfoString = JSON.stringify(userInfo);
  document.cookie = `userInfo=${userInfoString};path=/`;
}

In the above code, we define a function setUserInfoCookie that takes the user’s name, email, and age as parameters. We first create an object userInfo with these values and then serialize it into a string using JSON.stringify. Finally, we set a cookie with the name userInfo and value equal to userInfoString.