How to handle nested menu in knockout viewmodel - javascript

I am using knockoutjs in my project. I have a scenario where I have to create a nested menu in my viewmodel, which I did like this: = [
name: 'Services',
sub: [{ name: 'Service-A' }, { name: 'Service-B' }]
// etc
self.chosenMenu = ko.observable();
self.goToMenu = function (main, sub) {
var selectedMenu = {
main: main,
sub: sub
My View:
<ul class="nav navbar-nav menuitems col-md-8" data-bind="foreach: menu">
<li class="dropdown">
<a href="#" class="dropdown-toggle" data-toggle="dropdown">
<span data-bind="text: name"></span></a>
<ul class="dropdown-menu" role="menu" data-bind="foreach: sub">
<a href="javascript:void(0);" data-bind="text: name,
click: function() { $root.goToMenu($parent, $data); }">
However, I feel that this approach of creating nested menu is not good, because suppose if I want to go on any menu item programmatically then with his approach it is not possible?
Can anybody please suggest me the good approach to handle this kind of scenario?

Make sure each menu item has a unique identifier. For the example data you've given name will suffice, but you may have to add a fullPath property to menu item view models.
Your goToMenu function can now take just one parameter: uniqueMenuIdentifier, and recurse through all menu items to find the correct one, like this:
function findMenuItem(menuList, uniqueMenuIdentifier) {
for (var i = 0; i < menuList.length; i++) {
if (menuList[i].name === uniqueMenuIdentifier) {
return menuList[i];
if (!!menuList[i].sub) {
var subItem = findMenuItem(menuList[i].sub, uniqueMenuIdentifier);
if (!!subItem) {
return subItem;
return null;
self.goToMenu = function (menuItem) {
var uniqueMenuIdentifier =;
var item = findMenuItem(, uniqueMenuIdentifier);
This allows for a much simpler binding in the anchor tag:
<a href="javascript:void(0);" data-bind="text: name, click: $root.goToMenu">
See this fiddle for a demo.
From this you can also guess that it's even possible to set the chosenMenu directly:
// No longer needed:
//function findMenuItem(menuList, uniqueMenuIdentifier) { }
self.goToMenu = function (menuItem) {
See this fiddle for a demo.

I ran into a similar scenario yesterday. You can have a look at my solution on
Is there any knockout plugin for showing a nested context menu?. The main point is that I've used the template binding to be able to construct a hierarchical menu of any depth.


How do I add an attribute to an object within an observable array in knockout and trigger a notification?

With Knockout.js I have an observable array in my view model.
function MyViewModel() {
var self = this;
this.getMoreInfo = function(thing){
var updatedSport = jQuery.extend(true, {}, thing);
updatedThing.expanded = true;
this.aThing = {
theThings : ko.observableArray([{
id:1, expanded:false, anotherAttribute "someValue"
I then have some html that will change depending on the value of an attribute called "expanded". It has a clickable icon that should toggle the value of expanded from false to true (effectively updating the icon)
<div data-bind="foreach: aThing.theThings">
<div class="row">
<div class="col-md-12">
<!-- ko ifnot: $data.expanded -->
<i class="expander fa fa-plus-circle" data-bind="click: $parent.getMoreInfo"></i>
<!-- /ko -->
<!-- ko if: $data.expanded -->
<span data-bind="text: $data.expanded"/>
<i class="expander fa fa-minus-circle" data-bind="click: $parent.getLessInfo"></i>
<!-- /ko -->
<span data-bind="text: id"></span>
(<span data-bind="text: name"></span>)
Look at the monstrosity I wrote in the getMoreInfo() function in order to get the html to update. I am making use of the replace() function on observableArrays in knockout, which will force a notify to all subscribed objects. replace() will only work if the two parameters are not the same object. So I use a jQuery deep clone to copy my object and update the attribute, then this reflects onto the markup. My question is ... is there a simpler way to achieve this?
I simplified my snippets somewhat for the purpose of this question. The "expanded" attribute actually does not exist until a user performs a certain action on the app. It is dynamically added and is not an observable attribute in itself. I tried to cal ko.observable() on this attribute alone, but it did not prevent the need for calling replace() on the observable array to make the UI refresh.
Knockout best suits an architecture in which models that have dynamic properties and event handlers are backed by a view model.
By constructing a view model Thing, you can greatly improve the quality and readability of your code. Here's an example. Note how much clearer the template (= view) has become.
function Thing(id, expanded, name) {
// Props that don't change are mapped
// to the instance = id; = name;
// You can define default props in your constructor
// as well
this.anotherAttribute = "someValue";
// Props that will change are made observable
this.expanded = ko.observable(expanded);
// Props that rely on another property are made
// computed
this.iconClass = ko.pureComputed(function() {
return this.expanded()
? "fa-minus-circle"
: "fa-plus-circle";
}, this);
// This is our click handler
Thing.prototype.toggleExpanded = function() {
// This makes it easy to construct VMs from an array of data
Thing.fromData = function(opts) {
return new Thing(, opts.expanded, "Some name");
function MyViewModel() {
this.things = ko.observableArray(
id: 1,
expanded: false,
anotherAttribute: "someValue"
MyViewModel.prototype.addThing = function(opts) {
MyViewModel.prototype.removeThing = function(opts) {
var toRemove = this.things().find(function(thing) {
return ===;
if (toRemove) this.things.remove(toRemove);
var app = new MyViewModel();
// Add stuff later:
setTimeout(function() {
app.addThing({ id: 2, expanded: true });
app.addThing({ id: 3, expanded: false });
}, 2000);
setTimeout(function() {
app.removeThing({ id: 2, expanded: false });
}, 4000);
.fa { width: 15px; height: 15px; display: inline-block; border-radius: 50%; background: green; }
.fa-minus-circle::after { content: "-" }
.fa-plus-circle::after { content: "+" }
<script src=""></script>
<div data-bind="foreach: things">
<div class="row">
<div class="col-md-12">
<i data-bind="click: toggleExpanded, css: iconClass" class="expander fa"></i>
<span data-bind="text: id"></span> (
<span data-bind="text: name"></span>)

Knockoutjs binds correctly however href on a tag doesn't redirect to the page

I have this html:
<ul class="nav nav-tabs ilia-cat-nav" data-toggle="dropdown" data-bind="foreach : Items" style="margin-top:-30px">
<li role="presentation" data-bind="attr : {'data-id' : ID , 'data-childCount' : Children().length}" style="padding-left: 20px; padding-right: 20px; text-align: center; color: white" class="active-li">
<label id="menu1" data-toggle="dropdown" data-bind="text: Name"></label>
<ul class="dropdown-menu" data-bind="foreach: Children" role="menu" aria-labelledby="menu1">
<li role="presentation"><a role="menuitem" data-bind="text: Name, attr: { 'href': Url} "></a></li>
That creates my menu on top using knockoutjs, it works perfectly and href attribute on a tag is filled correctly like href="/site/models#{"catId": "76b4a8ed-1350-46af-8184-3b68029cbd22"}" however when i click on the item, it doesn't redirect to new page. my first thought was maybe its because of hash but it wasn't, so i tried to use target attribute for any of the _self and all others it doesn't work. so my next guess was that there is a javascript method overriding this, so far i haven't found anything. so my question is why doesn't it work?
KnockOut ViewModel:
landing.dataModels.Category = function (_id, _categoryTypeId, _name, _description, _parentId, _children) {
var self = this;
this.ID = ko.observable(_id);
this.CategoryTypeId = ko.observable(_categoryTypeId);
this.Name = ko.observable(_name);
this.Description = ko.observable(_description);
this.ParentId = ko.observable(_parentId);
this.Url = ko.computed(function () {
return '/site/models#{"catId": "' + self.ID() + '"}';
this.Children = ko.observableArray([]);
this.getChildren = ko.computed(function () {
return self.Children();
_.each(_children, function (item) {
self.Children.push(new landing.dataModels.Category(item.ID, item.categoryTypeId, item.Name, item.Description, item.ParentId, item.Children));
I have to say that when i right-click on the item and open in new window it does work and shows the page, but its not working on direct left click.
Probably the problem is in the quotes in the generated URL:
href="/site/models#{"catId": "76b4a8ed-1350-46af-8184-3b68029cbd22"}"
The value for href is actually "/site/models#{" leaving the rest of the URL as invalid HTML.
You could try to bind to the escaped URL:
this.Url = ko.computed(function () {
return encodeURI('/site/models#{"catId": "' + self.ID() + '"}');
Finally i got tired and i just went with a simple jquery click to make it work:
$(document).ready(function () {
setTimeout(function () {
$(document).on("click", ".ilia-catLink", function () {
var a = $(this).attr("href");
window.location = a;
}, 100);
It works this way, but i still wonder why wouldn't that href work on itself.

Function not able to access observableArray in knockout

I keep getting this error when I try to update an observableArray:
'Unable to get property 'removeAll' of undefined or null reference'
Here is my code:
var agilityFirmViewModel = {
test: ko.computed(function () {
return Pairs[0].Pairs;
currentLocation: ko.observableArray(Pairs[0].Pairs[0].Location);
//function to update values in currentLocation
ChangeLocation: function (practiceGroup) {
if (practiceGroup === undefined) {
practiceGroup = '(All Practice Groups)';
for (var i = 0; i <= Pairs[0].Pairs.length; i++) {
if (practiceGroup.Department === Pairs[0].Pairs[i].Department) {
return root.currentLocation;
$(document).ready(function () {
Assuming that it goes through the if statement inside the for loop everytime,
whenever it gets to
I get the error above saying that currentLocation is undefined. I know that currentLocation has data in it, so would could be causing this issue. It's probably something simple, but I can't seem to figure it out. Thank you.
Where i call ChangeLocation():
<li class="nav-sidebar-GreenMenu">
<a href="javascript:;" class="draggable-panel" draggable="true">
<i id="CategoryIcon" class="glyphicon glyphicon-user"></i>
<span class="sidebarTabName"><b>Practice Group</b></span><br />
<!--For some reason, changing the margin-left below will change the width of the entire sidebar-->
<span id="CurrentItem_TPG" class="currentItem" #*style="margin-left:64px;"*#>(All Practice Groups)</span>
<span id="DefaultItem_TPG" style="display:none;">(All Practice Groups)</span>
<i class="fa fa-chevron-left pull-right hidden-xs" data-bind=""></i>
<span class="arrow open" style="margin-top:-30px;"></span>
<ul class="sub-menu">
<!--ko foreach: test()-->
<!-- /ko -->
The problem is the way you're using bind. The actual signature for bind is:
fun.bind(thisArg[, arg1[, arg2[, ...]]])
Meaning, the first argument determines what this means in the function and the rest sets the arguments to use when it's called. Instead, try changing your click handler to this:
$parent.ChangeLocation.bind($parent, $data);
This ensures that ChangeLocation is called with $parent === this and $data === practiceGroup

Knockout: Can't get specific value from observableArray

I created array with data about some music albums in viewmodel. I can use this array in foreach loop (for example) but I can't display only one value from this array.
My viewmodel:
function CD(data) {
this.Author = ko.observable(data.Author);
this.Title = ko.observable(data.Title);
this.Price = ko.observable(data.Price);
this.Label = ko.observable(data.Label);
this.Id = ko.observable(data.Id);
function NewsListViewModel() {
var self = this;
self.newsList = ko.observableArray([]);
$.getJSON("/music/news", function (allData) {
var mapped = $.map(allData, function (item) { return new CD(item) });
self.oneObject = ko.computed(function () {
return self.newsList()[0].Title;
$(document).ready(function () {
ko.applyBindings(new NewsListViewModel());
And how I used it in html:
<ul data-bind="foreach: newsList">
<li data-bind="text: Title"></li>
<li data-bind="text: Author"></li>
<li data-bind="text: Price"></li>
<li data-bind="text: Label"></li>
This works perfectly. But if I trying additionally display one value:
<ul data-bind="foreach: newsList">
<li data-bind="text: Title"></li>
<li data-bind="text: Author"></li>
<li data-bind="text: Price"></li>
<li data-bind="text: Label"></li>
<p data-bind="text: oneObject"</p>
it dosen't working, firebug thrown error:
Type error: self.newsList()[0].Title is undefined
Why I cannot get one specific value but I can display whole list?
PS. Code <p data-bind="text: newsList()[0].Title"</p> didn't works too.
You get the error because $.getJSON is asynchronous.
So when your computed is declared your items are not necessary ready in the newsList so there is no first element what you could access.
So you need to check in your computed that your newsList is not empty (anyway your server could also return an empty list so it is always good to have this check) and only then access the first element:
self.oneObject = ko.computed(function () {
if (self.newsList().length > 0)
return self.newsList()[0].Title();
return 'no title yet';
Note: you need also write .Title() to get its value because Title is an observable.
I can see a few problems with your code:
$.getJSON is asynchronous so self.newsList is empty when it's accessed by Knockout for the first time. Which in turn means that self.newsList[0] is undefined.
return self.newsList()[0].Title; in the computed observable doesn't return the value you want it to return. It should be return self.newsList()[0].Title();
You don't have to reinvent the wheel, there is the mapping plugin which you can use to map the data:

Durandal 2.0 - Update the value of an observable in the view

I'm new to Durandal, my question has probably a very simple issue.
I load a list into a dropdown and the current value on the link which display the dropdown,
And the value of the link which display the dropdown is not updated correctly when an other value is selected.
But actually, I can't set the value of the observable in the select function.
View Model
var self = this;
self.system = require('durandal/system');
IPsKeys: ko.observableArray([]),
ipKeys: ko.observable(""),
activate: function (context) {
var that = this;
return $.when(
service.getIPSbyClientId(context.clientId).then(function (json) {
$.each(json, function (Index, Value) {
var ClientLobUWYear = {
NameLob: Value.LineOfBusiness.Name,
NameUWYear: Value.UnderwritingYear
if (Index=== 0) {
).then(function () {
//do some other datacontext calls for stuff used directly and only in view1
select: function (item) {
this.ipKeys = {
IdClient: item.IdClient,
IdLob: item.IdLob,
NameLob: item.NameLob,
NameUWYear: item.NameUWYear
/** Uncaught TypeError: undefined is not a function **/
<a id="select_lob-UWYear" class="dropdown-toggle" data-toggle="dropdown" href="#">
<span class="controls_value" data-bind="text: ipKeys().NameLob">ALOB</span>
<span class="controls_value" data-bind="text: ipKeys().NameUWYear">AYEAR</span>
<ul id="dropdown_year" class="dropdown-menu" data-bind="foreach: IPsKeys().sort(sortByLobYear)">
<a href="#" data-bind="click: $">
<span class="controls_value" data-bind="text: NameLob">Cargo</span>
<span class="controls_value" data-bind="text: NameUWYear">2014</span>
Thanks a lot
The way you update an observable is like this:
var someObservable = ko.observable(""); //setting to "";
someObservable("Something else"); //updating to "Something else"
Not like this (which you are doing above)
var someObservable = ko.observable(""); //setting to "";
someObservable = "Something else";
This is overwriting someObservable with a string of value "Something else" and so is no longer an observable which is why it will not update the ui.
[JS Fiddle showing how to set observables.]