I'm having trouble reading a cookie in javascript

Question

When there are multiple cookies on my site my javascript code doesn't work. I do not know how to specify the cookie name in javascript because i'm lacking expirience. The cookie is chancing the background color of the atricle.

Does someone know what i am doing wrong?

this is my code.

<div>
    <article id="bg">
        <h1>Kies een kleur en kijk wat voor cookie er wordt aangemaakt</h1>
        <select id="theme" onchange="setColorCookie()">
            <option value="Select Color">Kies een kleur</option>
            <option value="red">Rood</option>
            <option value="orange">Oranje</option>
            <option value="yellow">Geel</option>
            <option value="green">Groen</option>
            <option value="blue">Blauw</option>
            <option value="purple">Paars</option>
            <option value="pink">Roze</option>
            <option value="brown">Bruin</option>
            <option value="black">Zwart</option>
            <option value="white">Wit</option>
        </select>
    </article>
        <script type="text/javascript">
            window.onload = function ()
            {
                if (document.cookie.length != 0) {
                    var nameValueArray = document.cookie.split("=");
                    document.getElementById("theme").value = nameValueArray[1];
                    document.getElementById("bg").style.backgroundColor = nameValueArray[1];
                }
            }

            function setColorCookie()
            {
                var selectedValue = document.getElementById("theme").value;
                if (selectedValue != "Select Color")
                {
                    document.getElementById("bg").style.backgroundColor = selectedValue;
                    document.cookie = "color=" + selectedValue + ";expires=Fri, 5  2019 01:00:00 UTC;";
                }
            }
        </script>
    </div>

Answer 1

Look here: MDN: Document.cookie or here: JavaScript Cookies.

Instead of var nameValueArray = document.cookie.split("=");, you should do const myCookies = document.cookie.split(";");. Because:

https://developer.mozilla.org/en-US/docs/Web/API/Document/cookie

allCookies = document.cookie;

In the code above allCookies is a string containing a semicolon-separated list of all cookies (i.e. key=value pairs).

For example:

 allCookies = document.cookie;  // allCookies <= "cookie1=cow; cookie2 = pig; cookie3=  chicken;"
 cookiesArray = allCookies.split(';');  // cookiesArray[] <= ["cookie1=cow", "cookie2 = pig", "cookie3=  chicken"]

---

One more suggestion:

1. Modify your code like this:

   <script type="text/javascript">
       window.onload = function () {
           const allCookies = document.cookie;
           const cookiesArray = allCookies.split(';');
           alert('allCookies:' + allCookies);
           alert('cookiesArray:' + JSON.stringify(cookiesArray));
           if (document.cookie.length != 0) {
              ...
   

2. Re-run your program. When "onload()" triggers, you'll see two successive "alert" pop-ups.

   This should help better explain what's going on.

3. Please - PLEASE - post back if you have questions; if there's something you "don't get". This isn't a difficult concept - I definitely want you to understand it.

Answer 2

Take a look at w3schools:

function setCookie(cname, cvalue, exdays) {
  var d = new Date();
  d.setTime(d.getTime() + (exdays * 24 * 60 * 60 * 1000));
  var expires = "expires="+d.toUTCString();
  document.cookie = cname + "=" + cvalue + ";" + expires + ";path=/";
}

function getCookie(cname) {
  var name = cname + "=";
  var ca = document.cookie.split(';');
  for(var i = 0; i < ca.length; i++) {
    var c = ca[i];
    while (c.charAt(0) == ' ') {
      c = c.substring(1);
    }
    if (c.indexOf(name) == 0) {
      return c.substring(name.length, c.length);
    }
  }
  return "";
}

function checkCookie() {
  var user = getCookie("username");
  if (user != "") {
    alert("Welcome again " + user);
  } else {
    user = prompt("Please enter your name:", "");
    if (user != "" && user != null) {
      setCookie("username", user, 365);
    }
  }
}