override_fetch.js

(() => {
    let Store = {
        set:(key, object) => {
            var json = JSON.stringify(object);
            localStorage.setItem(key, json);
        },

        get: (key) => {
            var json = localStorage.getItem(key);
            return JSON.parse(json);
        }
    };

    let override = (object, methodName, callback) => {
        object[methodName] = callback(object[methodName])
    }

    let getTokenFromUser = () => {
        let savedToken = Store.get("token");

        if (savedToken) {
            return savedToken;
        } else {
            let token = prompt("What is your bearer token?");
            Store.set("token", token);
            return token;
        }
    };

    window.clearToken = () => {
        Store.set("token", null);
        getTokenFromUser();
    };

    override(window, "fetch", (original) => {
        return (url, params) => {
            let token = getTokenFromUser();
            params["headers"]["X-GraphiQL-Authorization"] = `Bearer ${token}`;
            return original.apply(this, [url, params]);
        }
    });
})();