ko.bindingHandlers.current.js

ko.bindingHandlers.current = {
    init: function(element, valueAccessor, allBindingsAccessor, viewModel) {
        ko.utils.registerEventHandler(element, 'click', function() {
            var observable = valueAccessor(), $element = $(element);

            $element.parent().children().removeClass('current');

            if (observable() === viewModel) {
                observable(null);
                return;
            }

            observable(viewModel);
            $element.addClass('current');
        });
    },

    update: function(element, valueAccessor, allBindingsAccessor, viewModel) {
        var value = ko.utils.unwrapObservable(valueAccessor()), $element;

        if (value === viewModel) {
            $element = $(element);
            $element.parent().children().removeClass('current');
            $element.addClass('current');
        }
    }
};