A cookie extender for Knockout JS

koCookieExtender.js

// Uses the cookie library at https://github.com/js-cookie/js-cookie

// Usage:  var firstName = ko.observable().extend({ cookie: "myFirstNameCookie" });

ko.extenders.cookie = function (target, option) {
    var cookieName = option;

    // Set the observable initially from the cookie value
    target(Cookies.get(cookieName));

    // Update the cookie when the observable updates
    target.subscribe(function (newValue) {
        Cookies.set(cookieName, newValue);
    });

    return target;
};