Learn How JavaScript Can Set and Retrieve Cookies with Examples

Table of content

  1. Introduction
  2. What are Cookies?
  3. How to Set Cookies with JavaScript
  4. Retrieving Cookies with JavaScript
  5. Example 1: Using Cookies to Store User Preferences
  6. Example 2: Implementing a Basic Shopping Cart with Cookies
  7. Security Considerations with Cookies
  8. Conclusion

Introduction

JavaScript is a powerful programming language that can help developers build interactive and dynamic websites. Cookies are one of the most important tools in web development, allowing websites to store information on a user's computer and retrieve it later. They are typically used to store user preferences, login credentials, shopping cart items and other such data. With JavaScript, you can easily set and retrieve cookies, making your website more functional and efficient.

Cookies are small text files that are stored on the user's computer by a web browser. They contain information that can be used by the website to personalize the user's experience, or to keep track of their browsing history. Cookies can be set with an expiry date, which means that they will only be active for a certain period of time. After that time, the cookie will be automatically deleted from the user's computer.

In JavaScript, the process of setting and retrieving cookies is fairly simple. Once you have a cookie set, you can use it to retrieve information about the user, such as their name, preferences, or any other data that you have stored. This data can be used to provide a more personalized browsing experience, such as showing them relevant products, customizing the layout of the website, or displaying customized messages based on their past behavior.

What are Cookies?

Cookies are small pieces of data that are stored on a user's computer by websites that are visited. Cookies are used to keep track of user preferences, login credentials, and other information that can help improve the user experience. Cookies can be set and retrieved by JavaScript code, making them a powerful tool for web developers.

Cookies are often created by web servers and sent to the user's browser as part of an HTTP response. Once a cookie is stored on a user's computer, it can be accessed and read by JavaScript running on the website. Cookies contain information such as a user's login status, shopping cart contents, or language preference – and this information can be used to create a more personalized user experience.

There are two types of cookies – session cookies and persistent cookies. Session cookies are stored in memory and are deleted when the user closes the browser. Persistent cookies, on the other hand, are stored on the user's computer and can last for a longer period of time – days, weeks or even months. Cookies can be used to track user behavior and preferences over time, allowing websites to provide a more personalized experience with improved usability.

JavaScript has APIs that enable developers to set and retrieve cookies. These APIs provide methods such as document.cookie and Cookie.parse for setting and retrieving cookies. By using these methods, developers can work with cookies in JavaScript and use them to create more advanced features and user experiences on their websites.

How to Set Cookies with JavaScript

To set cookies with JavaScript, you can use the document.cookie property. This property allows you to write a string of data to a user's browser that persists even after they've left your website. To set a cookie with JavaScript, you will need to provide a name and a value for the cookie. This is done by concatenating them with an equals sign, like this: document.cookie = "name=value".

It is important to note that cookies can also have additional properties such as an expiration date, a domain, and a path. To add an expiration date, you can simply add a expires property followed by a valid date that the cookie will expire on. For example, the following code snippet sets a cookie named "username" that expires in 30 days from the current date:

let d = new Date();
d.setTime(d.getTime() + (30*24*60*60*1000));
let expires = "expires="+ d.toUTCString();
document.cookie = "username=John Doe; " + expires;

To set a cookie that is only accessible from a specific domain and path, you can use the domain and path properties. For example, to set a cookie that is only accessible from the domain "example.com" and the path "/login", you can use the following code:

document.cookie = "username=John Doe; expires=Thu, 18 Dec 2024 12:00:00 UTC; domain=example.com; path=/login";

Overall, setting cookies with JavaScript can be a useful tool for storing a user's preferences or login information. By utilizing the document.cookie property and various cookie properties like expires, domain, and path, you can create a more personalized and customized experience for your website's visitors.

Retrieving Cookies with JavaScript

is a simple process that can be accomplished in just a few steps. Once a cookie has been set, it can be retrieved by accessing the "document.cookie" property. This property returns a string that contains all of the cookies associated with the current page.

To retrieve a specific cookie, we must first parse the "document.cookie" string. This can be done by splitting the string using the ";" character as the delimiter. Next, we iterate over each cookie and split it again using the "=" character as the delimiter. This will give us an array with two elements, the cookie name and its value.

We can then check if the cookie name matches the one we are looking for using an if statement. If it does, we can return the cookie value. If not, we continue iterating until we find the cookie we are looking for or until we have searched all of the cookies.

Here's an example of how to retrieve a cookie named "username":

function getCookie(name) {
  var cookies = document.cookie.split(';');
  for(var i = 0; i < cookies.length; i++) {
    var cookie = cookies[i].split('=');
    if(cookie[0].trim() === name) {
      return cookie[1];
    }
  }
  return '';
}

var username = getCookie('username');
console.log('Welcome back, ' + username + '!');

In this example, we define a function called "getCookie" that takes a cookie name as its parameter. Inside the function, we split the "document.cookie" string into an array of cookies and iterate over each one. For each cookie, we split it into its name and value and check if the name matches the one we are looking for. If it does, we return the cookie value. If not, we continue iterating.

Finally, we call the "getCookie" function with the name of the cookie we want and store the result in the "username" variable. We then log a welcome message to the console using the retrieved username.

In conclusion, is a straightforward process that involves parsing the "document.cookie" property and iterating over the resulting array. By understanding these concepts and using the steps outlined in this article, you can easily retrieve cookies with JavaScript and integrate them into your web applications.

Example 1: Using Cookies to Store User Preferences

To give you an idea of how cookies work in JavaScript, let’s take a look at an example of using cookies to store user preferences. Imagine you have a website where users can customize the layout and color scheme. In order to keep the user experience consistent across sessions, you want to store these preferences in a cookie.

First, you need to create the cookie with the user’s preferences. This can be done using the document.cookie property. Here’s an example of setting a cookie called user_preferences with the value of layout=vertical;color=blue:

document.cookie = "user_preferences=layout=vertical;color=blue";

Once the cookie has been set, you can retrieve the value of the cookie and use it to customize the website. Here’s an example of retrieving the user_preferences cookie and using it to set the layout and color scheme of the the web page:

let cookies = document.cookie.split('; ');
let userPreferences;
for (let i = 0; i < cookies.length; i++) {
    if (cookies[i].startsWith("user_preferences")) {
        userPreferences = cookies[i].split('=')[1];
    }
}
if (userPreferences && userPreferences.indexOf("layout=vertical") !== -1) {
    document.body.classList.add('vertical-layout');
}
if (userPreferences && userPreferences.indexOf("color=blue") !== -1) {
    document.body.style.backgroundColor = 'blue';
}

In this code, we start by splitting the document.cookie string into an array of individual cookies. We then iterate over each cookie and check if it is the user_preferences cookie. If it is, we extract the value of the cookie and store it in the userPreferences variable.

Next, we check the value of the userPreferences variable and use the classList and style properties of the DOM to apply the user’s preferences to the web page. If the user has selected a vertical layout, we add the vertical-layout class to the document.body element. If the user has selected a blue background color, we set the backgroundColor property of the document.body.style object to 'blue'.

In this way, we can use cookies to store user preferences and use them to customize the website experience. Keep in mind that cookies can be manipulated by the user, so you should always validate and sanitize any data that is stored in a cookie.

Example 2: Implementing a Basic Shopping Cart with Cookies

To implement a basic shopping cart with cookies in JavaScript, we can use the same concept of setting and retrieving cookies as in the previous example. First, we need to create a function that sets a cookie for the item that the user adds to their cart. We can do this by creating a loop that adds the item to the cookie if it doesn't already exist.

Once we've set the cookie for the item, we can retrieve that cookie whenever the user wants to view their cart. To do this, we can create another function that retrieves the cookie and displays the items in the user's cart. We can also create a function that removes an item from the cart by deleting the corresponding cookie.

Let's take a look at some example code:

function addToCart(item) {
  var cart = getCookie('cart');
  if (cart) {
    cart += ',' + item;
  } else {
    cart = item;
  }
  setCookie('cart', cart);
}

function viewCart() {
  var cart = getCookie('cart');
  if (cart) {
    var items = cart.split(',');
    for (var i = 0; i < items.length; i++) {
      console.log(items[i]);
    }
  } else {
    console.log('Your cart is empty.');
  }
}

function removeFromCart(item) {
  var cart = getCookie('cart');
  if (cart) {
    var items = cart.split(',');
    for (var i = 0; i < items.length; i++) {
      if (items[i] === item) {
        items.splice(i, 1);
        break;
      }
    }
    if (items.length > 0) {
      setCookie('cart', items.join(','));
    } else {
      deleteCookie('cart');
    }
  }
}

In this example, we have three functions: addToCart(), viewCart(), and removeFromCart(). The addToCart() function takes an item name as an argument and adds that item to the user's shopping cart. This is done by first checking if a cart cookie already exists. If it does, we add the item to the end of the cookie string. If it doesn't, we create a new cookie with just the item.

The viewCart() function displays the items in the user's cart. It does this by retrieving the cart cookie and splitting its contents into an array of item names. We then loop through that array and log each item to the console.

Finally, the removeFromCart() function removes an item from the user's cart. It does this by retrieving the cart cookie and splitting its contents into an array of item names. We then loop through that array looking for the item to remove. If we find it, we remove it from the array and update the cart cookie accordingly. If there are no items left in the cart after the removal, we delete the cart cookie altogether.

With these three functions, we can implement a basic shopping cart using cookies in JavaScript. By setting and retrieving cookies, we can keep track of which items the user has added to their cart and display them back to the user whenever they want to view their cart.

Security Considerations with Cookies

When working with cookies in JavaScript, it's important to consider security measures to protect sensitive information from unauthorized access. One important consideration is to avoid storing sensitive information in cookies, such as passwords or credit card numbers. Instead, store a reference to the information on the server-side, and retrieve it through an API call when needed.

Another security measure is to set the expiration date of cookies appropriately. A cookie with no expiration date can remain on the user's computer indefinitely, potentially providing a gateway for a malicious attacker. A shorter expiration date restricts the window of opportunity for attackers to access the information stored in the cookie.

It's also important to encrypt any sensitive information stored in a cookie to prevent unauthorized access. JavaScript provides options for encrypting cookies, such as using the window.crypto object for generating a unique encryption key for each session.

Additionally, it's important to verify the authenticity of the cookie to ensure that it has not been tampered with. This can be achieved by using a hash function to generate a checksum of the cookie data and comparing it to a stored checksum on the server-side. If the two do not match, the cookie has likely been tampered with and should be invalidated.

In summary, when working with cookies in JavaScript, it's important to consider security considerations to protect sensitive information from unauthorized access. These considerations include avoiding storing sensitive information in cookies, setting appropriate expiration dates, encrypting information in the cookie, and verifying the authenticity of the cookie.

Conclusion


In , understanding how to set and retrieve cookies using JavaScript is an essential skill for any web developer. Cookies can be used to store user preferences, track user behavior, and personalize the user experience. By using the document.cookie property and relevant methods such as split(), decodeURI(), and encodeURIComponent(), we can easily set and retrieve cookies in JavaScript.

It's important to remember that cookies have limitations and can be manipulated by users, so it's crucial to handle them securely and with caution. It's also important to note that with advancements in browser technology, alternative storage mechanisms such as localStorage and sessionStorage may be more suitable for specific use cases.

Overall, learning how to work with cookies in JavaScript is a valuable skill for any web developer. By following the examples and understanding the concepts outlined in this article, developers can confidently incorporate cookies into their web applications and provide a more personalized and engaging user experience.

As a seasoned software engineer, I bring over 7 years of experience in designing, developing, and supporting Payment Technology, Enterprise Cloud applications, and Web technologies. My versatile skill set allows me to adapt quickly to new technologies and environments, ensuring that I meet client requirements with efficiency and precision. I am passionate about leveraging technology to create a positive impact on the world around us. I believe in exploring and implementing innovative solutions that can enhance user experiences and simplify complex systems. In my previous roles, I have gained expertise in various areas of software development, including application design, coding, testing, and deployment. I am skilled in various programming languages such as Java, Python, and JavaScript and have experience working with various databases such as MySQL, MongoDB, and Oracle.
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