Develop Reference

KnockoutJS Assembling updated data from components

I am new to KnockoutJS.
I have an app that works in a following way:
when page is loaded a complex data structure is passed to frontend
this datastructure is splitted into smaller chunks and these chunks of data are passed to components
user interacts with components to edit chunks of data
upon clicking a button updated complex data structure should be passed to backend
I have troubles with a fourth step. I've been reading throught documentation and yet I couldn't figure out how I am supposed to get updated data.
Here is a JSFiddle: https://jsfiddle.net/vrggyf45
Here is the same code in snippet. See the bottom of the question for what I've tried.
ko.components.register('firstComponent', {
viewModel: function(params) {
var self = this;
self.firstComponentValue = ko.observable(params.firstComponentValue);
},
template: '<div><pre data-bind="text: JSON.stringify(ko.toJS($data), null, 2)"></pre><input data-bind="value: firstComponentValue, valueUpdate: \'afterkeydown\'"></div>'
});
ko.components.register('secondComponent', {
viewModel: function(params) {
var self = this;
self.secondComponentValue = ko.observable(params.secondComponentValue);
},
template: '<div><pre data-bind="text: JSON.stringify(ko.toJS($data), null, 2)"></pre><input data-bind="value: secondComponentValue, valueUpdate: \'afterkeydown\'"></div>'
});
var json = '{"items":[{"componentName":"firstComponent","firstComponentValue":"somevalue"},{"componentName":"secondComponent","secondComponentValue":"someothervalue"}]}';
var data = JSON.parse(json);
var mainVM = {};
mainVM.items = ko.observableArray(
ko.utils.arrayMap(data.items,
function(item) {
return ko.observable(item);
}));
ko.applyBindings(mainVM);
$('input[type=button]').click(function() {
var updatedData = ko.dataFor(document.getElementById('main'));
//get updated json somehow?
console.log(data);
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.4.2/knockout-min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="main">
<pre data-bind="text: JSON.stringify(ko.toJS($data), null, 2)"></pre>
<div data-bind="foreach: {data: items, as: 'item'}">
<hr>
<div data-bind="component: {name:componentName, params: item}">
</div>
</div>
<hr>
<input type="button" value="post data">
</div>
If I had a single view model I could have just used ko.dataFor($("#rootElement")) and send it to backend. However I intend to use components and they have their own viewmodels, which are not connected to the root viewmodel. I could have find them all with jQuery and use ko.dataFor but it looks like a big hack to me.
I also could have define all the viewmodels, including the components in the main viewmodel, but it makes components kind of useless.
Also I tried to change components viewmodels constructors so they would mutate input data and override incomming values with observables, but it seems like a hack to me as well.
Is there a function like ko.components or something that could give me all living viewmodels?

You can pass observables to the components so that their edits are immediately reflected in the parent object. ko.mapping is handy for converting plain JS objects to observables. Then when you want the data back, ko.toJS() it.
ko.components.register('firstComponent', {
viewModel: function(params) {
var self = this;
self.firstComponentValue = params.firstComponentValue;
},
template: '<div><pre data-bind="text: JSON.stringify(ko.toJS($data), null, 2)"></pre><input data-bind="value: firstComponentValue, valueUpdate: \'afterkeydown\'"></div>'
});
ko.components.register('secondComponent', {
viewModel: function(params) {
var self = this;
self.secondComponentValue = params.secondComponentValue;
},
template: '<div><pre data-bind="text: JSON.stringify(ko.toJS($data), null, 2)"></pre><input data-bind="value: secondComponentValue, valueUpdate: \'afterkeydown\'"></div>'
});
var json = '{"items":[{"componentName":"firstComponent","firstComponentValue":"somevalue"},{"componentName":"secondComponent","secondComponentValue":"someothervalue"}]}';
var data = JSON.parse(json);
var mainVM = {};
mainVM.items = ko.mapping.fromJS(data.items);
ko.applyBindings(mainVM);
$('input[type=button]').click(function() {
var updatedData = ko.toJS(ko.dataFor(document.getElementById('main')));
//Or, more simply: updatedData = ko.toJS(mainVM);
console.log(updatedData);
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.4.2/knockout-min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout.mapping/2.4.1/knockout.mapping.min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="main">
<pre data-bind="text: JSON.stringify(ko.toJS($data), null, 2)"></pre>
<div data-bind="foreach: {data: items, as: 'item'}">
<hr>
<div data-bind="component: {name:componentName, params: item}">
</div>
</div>
<hr>
<input type="button" value="post data">
</div>

Function bound to click action in foreach not being called

I'm having trouble binding my click action to the view model function to remove an item from an array (inside a foreach binding)
I've got the following view model
var FileGroupViewModel = function () {
var self = this;
self.files = ko.observableArray();
self.removeFile = function (item) {
self.files.remove(item);
}
self.fileUpload = function (data, e) {
var file = e.target.files[0];
self.files.push(file);
};
}
var ViewModel = function () {
var self = this;
self.FileGroup = ko.observableArray();
self.FileGroup1 = new FileGroupViewModel();
self.FileGroup2 = new FileGroupViewModel();
self.FileGroup3 = new FileGroupViewModel();
self.uploadFiles = function () {
alert("Uploading");
}
}
var viewModel = new ViewModel();
ko.applyBindings(viewModel);
And my view, which basically lists 3 "groups" of buttons, where a user can select files to upload
Everything below is working as expected, except $parent.removeFile isn't removing the file:
<div class="row files">
<h2>Files 1</h2>
<span class="btn btn-default btn-file">
Browse <input data-bind="event: {change: FileGroup1.fileUpload}" type="file" />
</span>
<br />
<div class="fileList" data-bind="foreach: FileGroup1.files">
<span data-bind="text: name"></span>
Remove
<br />
</div>
</div>
Fiddle at https://jsfiddle.net/alexjamesbrown/aw0798p7/
Am I wrong to do $parent.removeFile - it seems this doesn't get called on click?
This is a cut down working example, not the finished product!

You're misunderstanding $parent. It takes you out one context level. Your foreach uses FileGroup1.files as its index, so you might think that the $parent level would be Filegroup1, but it's not. It's the top-level viewmodel, because that is the context outside the foreach.
So your click binding should be
click: $parent.FileGroup1.removeFile

Knockout multiple click bindings do not work with IE8

The problem:
Multiple click binding do not work in IE8.
The code:
var Cart = function() {
var self = this;
self.books = ko.observableArray();
self.cds = ko.observableArray();
};
var TheModel = function() {
var self = this;
self.cart = ko.observable(new Cart());
self.showAddBook = function() {
self.cart.books.push(/* new book */);
};
self.showAddCD = function() {
self.cart.cds.push(/* new cd */);
};
};
<div data-bind="with: cart">
<h1>Books<h1>
<button data-bind="click: $parent.showAddBook">Add</button>
<div data-bind="foreach: books">
<span data-bind="text: name"></span> <!-- book has a name property -->
</div>
<hr/>
<h3>CDs</h3>
<button data-bind="click: $parent.showAddCD">Add</button>
<div data-bind="foreach: cds">
<span data-bind="text: name"></span> <!-- cd has a name property -->
</div>
</div>
Background:
Apologies in advance. I don't have access to jsFiddle at work.
I have a deadline to get this piece of work complete which is why I am using knockout with jQuery. Would love to use Angular but can't because we have to support IE8. Would love to use Durandal but I have no experience of it and don't have the time just yet to learn it and finish this piece of work.
A user can create a new book or a new cd and add it to a collection. Not real-world example but reflects the problem I am solving.
A user can click on an Add button, this launches a jQuery dialog which captures some information about a book. This is then saved to the observable array on the model, and the list of books gets updated.
Question:
Why does IE8 only seem to bind the first click and not the second? If I click to add a book the dialog is shown. If I click to add a cd, nothing. I have debugged and the function does not get called.
TIA

As far as I can tell, neither of them should work, and not on any browser (rather than just not working on IE8), because both functions have the same problem: They don't unwrap cart:
self.cart.books.push(/* new book */);
// ^^^^^^
cart is an observable, so you need:
self.cart().books.push(/* new book */);
// ^^
...and similarly for the CDs stuff.
If you fix that, it works (even on IE8):
var Cart = function() {
var self = this;
self.books = ko.observableArray();
self.cds = ko.observableArray();
};
var TheModel = function() {
var self = this;
self.cart = ko.observable(new Cart());
self.showAddBook = function() {
self.cart().books.push({name: "New book " + (+new Date())});
};
self.showAddCD = function() {
self.cart().cds.push({name: "New CD " + (+new Date())});
};
};
ko.applyBindings(new TheModel(), document.body);
<div data-bind="with: cart">
<h1>Books<h1>
<button data-bind="click: $parent.showAddBook">Add</button>
<div data-bind="foreach: books">
<span data-bind="text: name"></span> <!-- book has a name property -->
</div>
<hr/>
<h3>CDs</h3>
<button data-bind="click: $parent.showAddCD">Add</button>
<div data-bind="foreach: cds">
<span data-bind="text: name"></span> <!-- cd has a name property -->
</div>
</div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.2.0/knockout-min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>

Apologies for slightly incorrect example but I had missed one level of nesting. My example is not a true reflection of my complex model and implementation but I worked out the cause of the problem.
My Cart in this example has a selectedItem property (an observable) of type object that has the array of books (observable array) and CDs (observable array).
var Items = function () {
this.books = ko.observableArray();
this.cds = ko.observableArray();
}
var Cart = function() {
this.selectedItem = ko.observable(new Items());
}
var Model = function () {
this.cart = new Cart();
}
I was using the knockout 'with' binding and setting the context to cart.selectedItem
<div data-bind="with: cart.selectedItem"> ... </div>
With this approach I noticed that only the first click (add book) was working. Clicking on Add CD was doing nothing.
I changed the context from cart.selectedItem to cart and set the foreach binding (that displays the list of books and cds) to selectedItem().books and selectedItem().cds and that worked in IE8 and other browser.
If I change the context using the knockout 'with' binding back to cart.selectedItem then only the first click works.
Hope that helps anyone else who encounters this problem.

How can I copy this knockout observable?

I am trying to add a "default" object to my Knockout observableArray. The way my code stands currently, I end up adding the exact same object to the array instead of a new instance of the object. I tried using jQuery's .extend(), but, that didn't work out so I am looking for input.
Here is a demonstration to show my problem: http://jsfiddle.net/2c8Fx/
HTML:
<div data-bind="foreach: People">
<input type="text" data-bind="value: Name" />
</div>
<button type="button" data-bind="click: AddPerson">Add Person</button>
<pre data-bind="text: ko.toJSON($data, null, 2)"></pre>
Script:
function ViewModel() {
var self = this;
self.EmptyPerson = ko.mapping.fromJS({Name: null, Age: null});
self.People = ko.observableArray([self.EmptyPerson]);
self.AddPerson = function() {
self.People.push(self.EmptyPerson);
};
}
ko.applyBindings(new ViewModel());
This doesn't work because the observableArray is actually holding a reference to the same object for each index.
What's the best way to create a new instance of my Knockout object?

function ViewModel() {
var self = this;
self.People = ko.observableArray();
self.AddPerson = function() {
self.People.push(ko.mapping.fromJS({Name: null, Age: null}));
};
}
ko.applyBindings(new ViewModel());
I did this and it works like you think it would. I hope this helps.
Check out a working example here

Bind JSON with table in knockoutjs

how can i bind my json object with knockoutjs, here is my json :
"{\"Sport\":[{\"Name\":\"nana\",\"Description\":\"lmkmsdqd\",\"EndDate\":\"2012-07-22T00:00:00\"},
{\"Name\":\"sfqsdffqf\",\"Description\":\"lkqjskdlqsd\",\"EndDate\":\"2012-07-22T00:00:00\"}],
\"Music\":[{\,\"Name\":\"nana\",\"Description\":\"lmkmsdqd\",\"EndDate\":\"2012-07-22T00:00:00\"},
{\"Name\":\"sfqsdffqf\",\"Description\":\"lkqjskdlqsd\",\"EndDate\":\"2012-07-22T00:00:00\"}]}"
please suggest how can i bind it !!

Alright, so I put together a crude fiddle to demonstrate some binding concepts, as well as ViewModel construction. I had to clean up your JSON to do it. It demonstrates template, foreach, and text binding. If you haven't already done so, I highly recommend going through the tutorials on the knockout site.
Here are the HTML bindings:
Sports
<ul data-bind="template: { name: 'listingTemplate', foreach: sports}"></ul>
</br>
Music
<ul data-bind="template: { name: 'listingTemplate', foreach: music}"></ul>
<script type="text/html" id="listingTemplate">
<li>
<span data-bind="text: name"></span></br>
<span data-bind="text: description"></span></br>
<span data-bind="text: endDate"></span></br></br>
</li>
</script>​
and the viewmodels:
var Listing = function(data) {
this.name = ko.observable(data.Name || '');
this.description = ko.observable(data.Description|| '');
this.endDate = ko.observable(data.EndDate|| '');
};
var ViewModel = function(data) {
this.sports = ko.observableArray(
ko.utils.arrayMap(data.Sport, function(i) {return new Listing(i);})
);
this.music = ko.observableArray(
ko.utils.arrayMap(data.Music, function(i) {return new Listing(i);})
);
};