Edit in JSFiddle

/**
* Sets a Cookie with the given name and value.
*
* name       Name of the cookie
* value      Value of the cookie
* [expires]  Expiration date of the cookie (default: end of current session)
* [path]     Path where the cookie is valid (default: path of calling document)
* [domain]   Domain where the cookie is valid
*              (default: domain of calling document)
* [secure]   Boolean value indicating if the cookie transmission requires a
*              secure transmission
*/                        

function setCookie(name, value, expires, path, domain, secure) {
    document.cookie= name + "=" + escape(value) +
        ((expires) ? "; expires=" + expires.toGMTString() : "") +
        ((path) ? "; path=" + path : "") +
        ((domain) ? "; domain=" + domain : "") +
        ((secure) ? "; secure" : "");
}

/**
* Gets the value of the specified cookie.
*
* name  Name of the desired cookie.
*
* Returns a string containing value of specified cookie,
*   or null if cookie does not exist.
*/
function getCookie(name) {
    var dc = document.cookie;
    var prefix = name + "=";
    var begin = dc.indexOf("; " + prefix);
    if (begin == -1) {
        begin = dc.indexOf(prefix);
        if (begin != 0) return null;
    } else {
        begin += 2;
    }
    var end = document.cookie.indexOf(";", begin);
    if (end == -1) {
        end = dc.length;
    }
    return unescape(dc.substring(begin + prefix.length, end));
}

/**
* Deletes the specified cookie.
*
* name      name of the cookie
* [path]    path of the cookie (must be same as path used to create cookie)
* [domain]  domain of the cookie (must be same as domain used to create cookie)
*/
function deleteCookie(name, path, domain) {
    if (getCookie(name)) {
        document.cookie = name + "=" +
            ((path) ? "; path=" + path : "") +
            ((domain) ? "; domain=" + domain : "") +
            "; expires=Thu, 01-Jan-70 00:00:01 GMT";
    }
}










// setCookie() test
setCookie("CookieTest", "TestVal");
var setCookieSuccess = "Failed";
if(getCookie('CookieTest') === "TestVal"){
  setCookieSuccess = "Success";
}
console.log("setCookie('CookieTest', 'TestVal'): " + setCookieSuccess);

// getCookie() test
console.log("getCookie('CookieTest'): '" + getCookie('CookieTest') + "'");

// deleteCookie() test
deleteCookie("CookieTest");
var deleteCookieSuccess = "Failed";
if(getCookie('CookieTest') !== "TestVal"){
  deleteCookieSuccess = "Success";
}
console.log("deleteCookie('CookieTest'): " + deleteCookieSuccess);

<html>
<body>
  Check the console to see the test output.
</body>
</html>
body {
  font-family: arial;
}