JAVASCRIPT

remove cookie

function onRemoved(cookie) {
  console.log(`Removed: ${cookie}`);
}

function onError(error) {
  console.log(`Error removing cookie: ${error}`);
}

function removeCookie(tabs) {
  var removing = browser.cookies.remove({
    url: tabs[0].url,
    name: "favorite-color"
  });
  removing.then(onRemoved, onError);
}

var getActive = browser.tabs.query({active: true, currentWindow: true});
getActive.then(removeCookie);

for delete the cookie or destroy the cookie

setcookie("login","",time()-1);

delete cookie

document.cookie = "username=; expires=Thu, 01 Jan 1970 00:00:00 UTC; path=/;";

Remove Cookie

Cookie userNameCookieRemove = new Cookie("userName", "");
userNameCookieRemove.setMaxAge(0);
response.addCookie(userNameCookieRemove);