Extension method for Knockout that enables an Errors collection on observables

gistfile1.txt

(function (ko, undefined) {

    ko.observable.fn.withValidation = function () {
        var observable = this;
        observable.Errors = ko.observableArray();
        observable.HasErrors = ko.computed(function () {
            return observable.Errors().length > 0;
        });
        return observable;
    };

} (ko));