Knockout.js custom binding handler to show / hide an element with jQuery's slideUp / slideDown methods

bindinghandler.js

ko.bindingHandlers.slideToggleVisible = {
    init: function(element, valueAccessor) {
        var value = valueAccessor();
        ko.unwrap(value) ? $(element).show() : $(element).hide();
    },
    update: function(element, valueAccessor) {
        var value = valueAccessor();
        ko.unwrap(value) ? $(element).slideDown() : $(element).slideUp();
    }
};

Usage:

<div data-bind="slideToggleVisible: expanded">

while expanded is an observable returning the current visible state of the element.