create and retrieve cookies

cookies.js

function utmCookieTag() {

    const queryString = window.location.search; //  url query string
    const urlParams = new URLSearchParams(queryString); // get parameters in  url
    // get required parameters for the cookie management
    const utm_medium_value = urlParams.get('utm_medium')
    
    if (utm_medium_value) {
        const previousCookie = getCookie("_utmMedium"); // check for previous cookie
        if (previousCookie) {
            // if prev cookie exists, get expiration date from _expireUtmMedium cookie
            let prevExpDate = getCookie("_expireUtmMedium");
            let exDate =new Date(prevExpDate); // Date conversion
            const updated_utm_medium_value = previousCookie + ":" + utm_medium_value; // concat new utm_medium value to prev cookie
            setCookie("_utmMedium", updated_utm_medium_value, exDate);
         } else {
            let exDate = getExpirationDate(14);
            setCookie("_utmMedium", utm_medium_value, exDate) // create new _utmMedium cookie
            setCookie("_expireUtmMedium", exDate, exDate); // create _expireUtmMedium to keep track of expiration date
        }
    }
}

// expiration date from number of days
function getExpirationDate(exdays){
    const d = new Date();
    d.setTime(d.getTime() + (exdays * 24 * 60 * 60 * 1000));
    return d;
}

// create cookie
function setCookie(cname, cvalue, date) {
    let expires = "expires=" + date.toUTCString();
    document.cookie =cname + "=" + cvalue + ";" + expires + ";path=/";
}  


// retrieve cookie
function getCookie(cname) {
    let name = cname + "=";
    
    let decodedCookie = decodeURIComponent(document.cookie);
    let ca = decodedCookie.split(';');
    console.log("ca: " + ca)
    for (let i = 0; i < ca.length; i++) {
        let c = ca[i];
        while (c.charAt(0) == ' ') {
            c = c.substring(1);
        }
        if (c.indexOf(name) == 0) {
            console.log(c);
            return c.substring(name.length, c.length);
        }
    }
    return "";
}