Today we'll be looking into working with Cookies in JavaScript. It's not the most widely used function, but great to keep track of small things like whether someone clicked a cookie bar.

We can set, get, change and, delete a cookie.

JavaScript Set Cookie

To set a cookie in JavaScript, we use the document.cookie property.

First we must understand cookies are set as a key, value pair

key = value

So to set a cookie:

document.cookie = 'username=Chris';

We can even set a expire date:

document.cookie = 'username=Chris; expires=Sun, 01 Jan 2023 12:00:00 UTC';

JavaScript Read Cookie

To read a cookie we can use the following:

var username = document.cookie;
username = Chris;
second = bla;

This will return the full cookie object, so we need to split it ourself like so:

var username = getCookie('username');
console.log(username);
// Chris

function getCookie(name) {
  // Add the = sign
  name = name + '=';

  // Get the decoded cookie
  var decodedCookie = decodeURIComponent(document.cookie);

  // Get all cookies, split on ; sign
  var cookies = decodedCookie.split(';');

  // Loop over the cookies
  for (var i = 0; i < cookies.length; i++) {
    // Define the single cookie, and remove whitespace
    var cookie = cookies[i].trim();

    // If this cookie has the name of what we are searching
    if (cookie.indexOf(name) == 0) {
      // Return everything after the cookies name
      return cookie.substring(name.length, cookie.length);
    }
  }
}

JavaScript Changing a Cookie

Sometimes we want to update a cookie; this is the same as the creation:

document.cookie = 'username=Nicole; expires=Sun, 01 Jan 2023 12:00:00 UTC';

JavaScript Deleting a Cookie

To delete a specific cookie, we have to set its date to be passed:

document.cookie = 'username=; expires=Thu, 01 Jan 1970 00:00:00 UTC;';

View the demo to test with on Codepen.

View on Codepen.

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