cache.js
import { InMemoryCache, makeVar } from '@apollo/client';

const isLoggedIn = () => Cookies.get('TOKEN');

export const isUserLoggedInVar = makeVar(isLoggedIn());

const cache = new InMemoryCache({
  typePolicies: {
    Query: {
      fields: {
        readNumOfOutofStockItems: {
          read(cart, { readField }) {
            // logic of OutofStock items
          }
        },
        isUserLoggedIn: {
          read() {
            return isUserLoggedInVar();
          }
        }
      }
    }
  }

const client = new ApolloClient({ cache });

Gets the 'token' cookie

How we create

reactive var

How we declare

reactive var

here