j.js

ko.bindingHandlers.slideVisible = {
    init: function(element, valueAccessor) {
        var value = ko.utils.unwrapObservable(valueAccessor()); // Get the current value of the current property we're bound to
        $(element).toggle(value); // jQuery will hide/show the element depending on whether "value" or true or false
    },
    update: function(element, valueAccessor, allBindingsAccessor) {
        // Leave as before
    }
};