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AngularJS ng-repeat is slow

It is not like it is slow on rendering many entries. The problem is that whenever the $scope.data got updated, it adds the new item first at the end of the element, then reduce it as it match the new $scope.data.
For example:
<div class="list" ng-repeat="entry in data">
<h3>{{entry.title}}</h3>
</div>
This script is updating the $scope.data:
$scope.load = function() {
$scope.data = getDataFromDB();
}
Lets say I have 5 entries inside $scope.data. The entries are:
[
{
id: 1,
title: 1
},
{
id: 2,
title: 2
},
......
]
When the $scope.data already has those entries then got reloaded ($scope.data = getDataFromDB(); being called), the DOM element for about 0.1s - 0.2s has 10 elements (duplicate elements), then after 0.1s - 0.2s it is reduced to 5.
So the problem is that there is delay about 0.1s - 0.2s when updating the ng-repeat DOM. This looks really bad when I implement live search. Whenever it updates from the database, the ng-repeat DOM element got added up every time for a brief millisecond.
How can I make the rendering instant?
EDITED
I will paste all my code here:
The controller:
$scope.search = function (table) {
$scope.currentPage = 1;
$scope.endOfPage = false;
$scope.viewModels = [];
$scope.loadViewModels($scope.orderBy, table);
}
$scope.loadViewModels = function (orderBy, table, cb) {
if (!$scope.endOfPage) {
let searchKey = $scope.page.searchString;
let skip = ($scope.currentPage - 1) * $scope.itemsPerPage;
let searchClause = '';
if (searchKey && searchKey.length > 0) {
let searchArr = [];
$($scope.vmKeys).each((i, key) => {
searchArr.push(key + ` LIKE '%` + searchKey + `%'`);
});
searchClause = `WHERE ` + searchArr.join(' OR ');
}
let sc = `SELECT * FROM ` + table + ` ` + searchClause + ` ` + orderBy +
` LIMIT ` + skip + `, ` + $scope.itemsPerPage;
sqlite.query(sc, rows => {
$scope.$apply(function () {
var data = [];
let loadedCount = 0;
if (rows != null) {
$scope.currentPage += 1;
loadedCount = rows.length;
if (rows.length < $scope.itemsPerPage)
$scope.endOfPage = true
for (var i = 0; i < rows.length; i++) {
let item = rows.item(i);
let returnObject = {};
$($scope.vmKeys).each((i, key) => {
returnObject[key] = item[key];
});
data.push(returnObject);
}
$scope.viewModels = $scope.viewModels.concat(data);
}
else
$scope.endOfPage = true;
if (cb)
cb(loadedCount);
})
});
}
}
The view:
<div id="pageContent" class="root-page" ng-controller="noteController" ng-cloak>
<div class="row note-list" ng-if="showList">
<h3>Notes</h3>
<input ng-model="page.searchString" id="search"
ng-keyup="search('notes')" type="text" class="form-control"
placeholder="Search Notes" style="margin-bottom:10px">
<div class="col-12 note-list-item"
ng-repeat="data in viewModels track by data.id"
ng-click="edit(data.id)"
ontouchstart="touchStart()" ontouchend="touchEnd()"
ontouchmove="touchMove()">
<p ng-class="deleteMode ? 'note-list-title w-80' : 'note-list-title'"
ng-bind-html="data.title"></p>
<p ng-class="deleteMode ? 'note-list-date w-80' : 'note-list-date'">{{data.dateCreated | displayDate}}</p>
<div ng-if="deleteMode" class="note-list-delete ease-in" ng-click="delete($event, data.id)">
<span class="btn fa fa-trash"></span>
</div>
</div>
<div ng-if="!deleteMode" ng-click="new()" class="add-btn btn btn-primary ease-in">
<span class="fa fa-plus"></span>
</div>
</div>
<div ng-if="!showList" class="ease-in">
<div>
<div ng-click="back()" class="btn btn-primary"><span class="fa fa-arrow-left"></span></div>
<div ng-disabled="!isDataChanged" ng-click="save()" class="btn btn-primary" style="float:right">
<span class="fa fa-check"></span>
</div>
</div>
<div contenteditable="true" class="note-title"
ng-bind-html="selected.title" id="title">
</div>
<div contenteditable="true" class="note-container" ng-bind-html="selected.note" id="note"></div>
</div>
</div>
<script src="../js/pages/note.js"></script>
Calling it from:
$scope.loadViewModels($scope.orderBy, 'notes');
The sqlite query:
query: function (query, cb) {
db.transaction(function (tx) {
tx.executeSql(query, [], function (tx, res) {
return cb(res.rows, null);
});
}, function (error) {
return cb(null, error.message);
}, function () {
//console.log('query ok');
});
},
It is apache cordova framework, so it uses webview in Android emulator.
My Code Structure
<html ng-app="app" ng-controller="pageController">
<head>....</head>
<body>
....
<div id="pageContent" class="root-page" ng-controller="noteController" ng-cloak>
....
</div>
</body>
</html>
So there is controller inside controller. The parent is pageController and the child is noteController. Is a structure like this slowing the ng-repeat directives?
Btw using track by is not helping. There is still delay when rendering it. Also I can modify the entries as well, so when an entry was updated, it should be updated in the list as well.
NOTE
After thorough investigation there is something weird. Usually ng-repeat item has hash key in it. In my case ng-repeat items do not have it. Is it the cause of the problem?

One approach to improve performance is to use the track by clause in the ng-repeat expression:
<div class="list" ng-repeat="entry in data track by entry.id">
<h3>{{entry.title}}</h3>
</div>
From the Docs:
Best Practice: If you are working with objects that have a unique identifier property, you should track by this identifier instead of the object instance, e.g. item in items track by item.id. Should you reload your data later, ngRepeat will not have to rebuild the DOM elements for items it has already rendered, even if the JavaScript objects in the collection have been substituted for new ones. For large collections, this significantly improves rendering performance.
For more information, see
AngularJS ngRepeat API Reference -- Tracking and Duplicates

In your html, try this:
<div class="list" ng-repeat="entry in data">
<h3 ng-bind="entry.title"></h3>
</div>

After thorough research, I found my problem. Every time I reset / reload my $scope.viewModels I always assign it to null / empty array first. This what causes the render delay.
Example:
$scope.search = function (table) {
$scope.currentPage = 1;
$scope.endOfPage = false;
$scope.viewModels = []; <------ THIS
$scope.loadViewModels($scope.orderBy, table);
}
So instead of assigning it to null / empty array, I just replace it with the new loaded data, and the flickering is gone.

How to filter data on screen with ajax using dropdown list? [duplicate]

In a MVC partial view file, I build one Html.TextBox and two submit buttons. These two buttons will increase/decrease the Html.TextBox value once clicked. The Html.TextBox displayed value will change accordingly.However, once I need to update the #refTable div based on the new value after click. The page or section never updated. Codes are below, where some comments are added for explanation purpose. Thanks for your help.
//******* cshtml file **********//
<body>
</body>
<input type="submit" value="PrevY" name="chgYr2" id="pY" />
#{
var tempItem3 = Model.First(); // just give the first entry from a database, works.
if (ViewData["curSel"] == null)
{
#Html.TextBox("yearSelect3", Convert.ToDateTime(tempItem3.Holiday_date).Year.ToString());
ViewBag.selYear = Convert.ToDateTime(tempItem3.Holiday_date).Year; // just initial value, works
ViewData["curSel"] = Convert.ToDateTime(tempItem3.Holiday_date).Year;
}
else
{
#Html.TextBox("yearSelect3", ViewData["curSel"].ToString());
}
}
<input type="submit" value="NextY" name="chgYr2" id="nY" />
<script type="text/javascript">
$(document).ready(function () {
$(document).on("click", "#nY", function () {
var val = $('#yearSelect3').val();
$('#yearSelect3').val((val * 1) + 1);
var dataToSend = {
id: ((val * 1) + 1)
}
// add some jquery or ajax codes to update the #refTable div
// also ViewBag.selYear need to be updated as ((val * 1) + 1)
// like: ViewBag.selYear = ((val * 1) + 1);
// any similar temp variable is fine
});
});
$(document).on("click", "#pY", function () {
var val = $('#yearSelect3').val();
$('#yearSelect3').val((val * 1) - 1);
var dataToSend = {
id: ((val * 1) - 1)
}
});
});
</script>
<span style="float: right">Set Holiday Calender for 2013</span>
<span id="btnAddHoliday">#Html.ActionLink("Add Holiday", "Create", null, new { id = "addHilBtn" })</span>
<div id="refTable">
<table class="tblHoliday" style="width: 100%;">
<th>
Holiday
</th>
<th>
Dates
</th>
<th>Modify</th>
<th>Delete</th>
</tr>
#foreach (var item in Model)
{
if ( Convert.ToDateTime(item.Holiday_date).Year == ViewBag.selYear)
// if the ViewBag.selYear is hard code, this selection "works"
{
<tr>
<td>
#Html.DisplayFor(modelItem => item.Holiday_Name)
</td>
<td>
#item.Holiday_date.Value.ToString("MM/dd/yyyy")
</td>
<td>
#Html.ActionLink("Edit", "Edit", new { })
</td>
<td>
#Html.ActionLink("Delete", "Delete", new { })
</td>
</tr>
}
}
</table>
</div>

You'll need AJAX if you want to update a part of your page without reloading the entire page.
main cshtml view
<div id="refTable">
<!-- partial view content will be inserted here -->
</div>
#Html.TextBox("yearSelect3", Convert.ToDateTime(tempItem3.Holiday_date).Year.ToString());
<button id="pY">PrevY</button>
<script>
$(document).ready(function() {
$("#pY").on("click", function() {
var val = $('#yearSelect3').val();
$.ajax({
url: "/Holiday/Calendar",
type: "GET",
data: { year: ((val * 1) + 1) }
})
.done(function(partialViewResult) {
$("#refTable").html(partialViewResult);
});
});
});
</script>
You'll need to add the fields I have omitted. I've used a <button> instead of submit buttons because you don't have a form (I don't see one in your markup) and you just need them to trigger javascript on the client side.
The HolidayPartialView gets rendered into html and the jquery done callback inserts that html fragment into the refTable div.
HolidayController Update action
[HttpGet]
public ActionResult Calendar(int year)
{
var dates = new List<DateTime>() { /* values based on year */ };
HolidayViewModel model = new HolidayViewModel {
Dates = dates
};
return PartialView("HolidayPartialView", model);
}
This controller action takes the year parameter and returns a list of dates using a strongly-typed view model instead of the ViewBag.
view model
public class HolidayViewModel
{
IEnumerable<DateTime> Dates { get; set; }
}
HolidayPartialView.csthml
#model Your.Namespace.HolidayViewModel;
<table class="tblHoliday">
#foreach(var date in Model.Dates)
{
<tr><td>#date.ToString("MM/dd/yyyy")</td></tr>
}
</table>
This is the stuff that gets inserted into your div.

The main concept of partial view is returning the HTML code rather than going to the partial view it self.
[HttpGet]
public ActionResult Calendar(int year)
{
var dates = new List<DateTime>() { /* values based on year */ };
HolidayViewModel model = new HolidayViewModel {
Dates = dates
};
return PartialView("HolidayPartialView", model);
}
this action return the HTML code of the partial view ("HolidayPartialView").
To refresh partial view replace the existing item with the new filtered item using the jQuery below.
$.ajax({
url: "/Holiday/Calendar",
type: "GET",
data: { year: ((val * 1) + 1) }
})
.done(function(partialViewResult) {
$("#refTable").html(partialViewResult);
});

You can also use Url.Action for the path instead like so:
$.ajax({
url: "#Url.Action("Holiday", "Calendar", new { area = "", year= (val * 1) + 1 })",
type: "GET",
success: function (partialViewResult) {
$("#refTable").html(partialViewResult);
}
});

Infinite scrolling fills completely rather than incrementally

I am attempting to create infinite scrolling on my web page using an example I found. However, the page fills up completely with all the items instead of just showing several items at a time. In other words it is not doing infinite scrolling. I noticed in some of the examples they parsed out data in chunks but in the real world how are you supposed to do that?
Below is my html code:
<table class="table table-striped table-bordered"><tr>
<th style="text-align:center;">User ID</th> <th>Username</th><th>Rank</th>
<th>Posts</th><th>Likes</th> <th>Comments</th> <th>Flags</th><th>Status</th><th>Action</th></tr>
<tr><td class="center">
<div ng-app='scroll' ng-controller='Scroller'>
<div when-scrolled="loadMore("")">
<div ng-repeat='item in items'>
<span>{{item.id}}
<span style="position:absolute;left:140px;">{{item.username}}</span>
<span style="position:absolute;left:290px;">{{item.rank}}</span>
<span style="position:absolute;left:360px;">{{item.posts}}</span>
<span style="position:absolute;left:440px;">{{item.likes}}</span>
<span style="position:absolute;left:530px;">{{item.comments}}</span>
<span style="position:absolute;left:640px;">{{item.flags}}</span>
<span class="label label-success" style="position:absolute;left:710px;">Active</span>
<a style="position:absolute;left:790px;" class="btn btn-info" style="width:30px" ng-href='/admin/userDetail?userid={{item.id}}'>
View Detail</a>
<hr>
</div>
</div>
</div>
</td></tr>
</table>
Below is my angularjs code:
function Scroller($scope, $http, $q, $timeout) {
$scope.items = [];
var lastuser = '999999';
$scope.loadMore = function(type) {
todate = document.getElementById("charttype").value;
var url = "/admin/getusers?type=" + todate + "&lastuser=" + lastuser;
var d = $q.defer();
$http({
'url': url,
'method': 'GET'
})
.success(function (data) {
var items = data.response;
for (var i = $scope.items.length; i < items.length; i++) {
$scope.items.push(items[i]);
count++;
if (count > 100)
{
lastuser = $scope.items[i].id;
break;
}
d.resolve($scope.items);
d.promise.then(function(data) {
});
}
)
.error(function (data) {
console.log(data);
});
return d.promise;
};
$scope.loadMore();
}
angular.module('scroll', []).directive('whenScrolled', function() {
return function(scope, elm, attr) {
var raw = elm[0];
alert("scroll");
elm.bind('scroll', function() {
if (raw.scrollTop + raw.offsetHeight >= raw.scrollHeight) {
scope.$apply(attr.whenScrolled);
}
});
};
});
My question is why does my web page show all 3200 lines initially rather than allowing me to do infinite scrolling. You will notice I put an alert in the scroll module and it is never displayed. Do I have to incrementally read my database? Any help is appreciated.

You are adding all of the items returned from your API call into $scope.items.
for (var i = 0; i < items.length; i++) {
$scope.items.push(items[i]);
}
Don't you want to add only a subset of those items?
P.S. Might help if you create a Plunkr to show the specific problem.
EDIT:
Based on your comment about the directive not working, I put together this Plunkr, which is a copy of your code but with the $http get code ripped out. The "scroll" alert fires here. I think you're just missing a closing bracket on your for loop (since I don't have your API endpoint to test against, I can't actually run your code live).
EDIT 2:
I'm not sure why you aren't seeing the function fire correctly on scroll. I've set up another plunker where I've changed the result of the scroll event firing to show an alert and load more items from a data variable, so you can see that the scroll event is firing correctly and it will load more items.

Knockout JS Binding Null Binding

Here is a fiddle
I have this html:
<div class="margin:0px; padding:0px; outline:0; border:0;" data-bind="with: notesViewModel">
<table class="table table-striped table-hover" data-bind="with: notes">
<thead><tr><th>Date Logged</th><th>Content</th><th>Logged By</th><th></th></tr>
</thead>
<tbody data-bind="foreach: allNotes">
<tr>
<td data-bind="text: date"></td>
<td data-bind="text: compressedContent"></td>
<td data-bind="text: logged"></td>
<td><img src="/images/detail.png" data-bind="click: $root.goToNote.bind($data, $index())" width="20" alt="Details"/></td>
</tr>
</tbody>
</table>
<div class="noteView" data-bind="with: chosenNote">
<div class="info">
<p><label>Date:</label><span data-bind="text: date"></span></p>
<p><label>Logged:</label><span data-bind="text: logged"></span></p>
</div>
<p class="message" data-bind="html: content"></p>
<button class="btn btn-default" data-bind="click: $root.toNotes">Back to Notes</button>
</div>
<div class="editor-label" style="margin-top:10px">
Notes
</div>
<div class="editor-field">
<textarea id="contact_note" rows="5" class="form-control" data-bind="value: $root.noteContent"></textarea>
<p data-bind="text: $root.characterCounter"></p>
<button class="btn btn-info" data-bind="click: $root.saveNotes">Save</button>
<div data-bind="html: $root.status">
</div>
</div>
</div>
And this JavaScript using knockout:
var notesViewModel = function () {
var self = this;
self.notes = ko.observable(null);
self.chosenNote = ko.observable();
self.allNotes = new Array();
self.user = "user1";
// behaviours
self.goToNote = function (noteIndex) {
self.notes(null);
self.chosenNote(new note(self.allNotes[noteIndex]));
};
self.toNotes = function () {
self.chosenNote(null);
self.notes({ allNotes: $.map(self.allNotes, function (item) { return new note(item); }) });
console.log(self.notes());
}
self.noteContent = ko.observable();
self.saveNotes = function () {
var request = $.ajax({
url: "EnquiryManagement/Contact/SaveNotes",
type: "GET",
dataType: "json",
data: { id: "1322dsa142d2131we2", content: self.noteContent() }
});
request.done(function (result, message) {
var mess = "";
var err = false;
var imgSrc = "";
if (message = "success") {
if (result.success) {
mess = "Successfully Updated";
imgSrc = "/images/tick.png";
self.allNotes.push({ date: new Date().toUTCString(), content: self.noteContent(), logged: self.user });
self.toNotes();
} else {
mess = "Server Error";
imgSrc = "/images/redcross.png";
err = true;
}
} else {
mess = "Ajax Client Error";
imgSrc = "/images/redcross.png";
err = true;
}
self.status(CRTBL.CreateMessageOutput(err, mess, imgSrc));
self.noteContent(null);
setTimeout(function () {
self.status(null);
}, 4000);
});
};
self.status = ko.observable();
self.characterCounter = ko.computed(function () {
return self.noteContent() == undefined ? 0 : self.noteContent().length;
});
};
var note = function (data) {
var self = this;
console.log(data.date);
self.date = CRTBL.FormatIsoDate(data.date);
self.content = data.content;
self.compressedContent = data.content == null ? "" : data.content.length < 25 ? data.content : data.content.substring(0, 25) + " ...";
self.logged = data.logged;
console.log(this);
};
ko.applyBindings(new notesViewModel());
When I first load the page it says:
Uncaught Error: Unable to parse bindings.
Message: ReferenceError: notes is not defined;
Bindings value: with: notes
However, I pass it null, so it shouldn't show anything, because when I do the function goToNote then do goToNotes it sets the notes observable to null
So why can't I start off with this null value?

The problem is where you have:
<div data-bind="with: notesViewModel">
That makes it look for a property "notesViewModel" within your notesViewModel, which does not exist.
If you only have one view model you can just remove that data binding and it will work fine.
If, however, you wish to apply your view model to just that div specifically and not the entire page, give it an ID or some other form of accessor, and add it as the second parameter in applyBindings, as follows:
HTML:
<div id="myDiv">
JS:
ko.applyBindings(new notesViewModel(), document.getElementById('myDiv'));
This is generally only necessary where you have multiple view models in the same page.

Like what bcmcfc has put, however, due to my scenario being a multi-viewModel scenario I don't think his solution is quite the right one.
In order to achieve the correct results, first of all I extrapolated out the self.notes = ko.observable(null); into a viewModel which makes doing the table binding far easier.
Then to fix the binding issues instead of setting an element for the bind to take place, I merely did this:
ko.applyBindings({
mainViewModel: new mainViewModel(),
notesViewModel: new notesViewModel()
});
In my original code I have two viewModels which is why I was getting this error. With this method the key is:
I don't create dependancies!
Instead of tieing the viewModel to a certain dom element which can change quite easily and cause having to go and changes things with ko, plus if I add more viewModels then it can get more complicated. I simply do:
data-bind="with: viewModel"
That way I can bind to any DOM object and I can have has many as I like.
This is the solution that solved my post.
Here is the jsfiddle

knockout.js - deferred databinding for modal?

I am using knockout.js to display a list of employees. I have a single hidden modal markup on the page. When the "details" button for a single employees is clicked, I want to data-bind that employee to the modal popup. I am using the ko.applyBindings(employee, element) but the problem is when the page loads, it is expecting the modal to start off as bound to something.
So I'm wondering, is there a trick/strategy to do a late/deferred databinding? I looked into virtual bindings but the documentation was not helpful enough.
Thanks!

I would like to propose a different way to work with modals in MVVVM. In MVVM, the ViewModel is data for the View, and the View is responsible for the UI. If we examine this proposal:
this.detailedEmployee = ko.observable({}),
var self = this;
this.showDetails = function(employee){
self.detailedEmployee(employee);
$("#dialog").dialog("show"); //or however your dialog works
}
I strongly agree with this.detailedEmployee = ko.observable({}), but I am in strong disagreement with this line: $("#dialog").dialog("show");. This code is placed in the ViewModel and shows the modal window, wherein fact it is View's responsibility, so we screw-up the MVVM approach. I would say this piece of code will solve your current task but it could cause lots of problems in future.
When closing the popup, you should set detailedEmployee to undefined to have your main ViewModel in a consistent state.
When closing the popup, you might want to have validation and the possibility to discard the close operation when you want to use another modal's component in the application
As for me, these points are very critical, so I would like to propose a different way. If we "forget" that you need to display data in popup, binding with could solve your issue.
this.detailedEmployee = ko.observable(undefined);
var self = this;
this.showDetails = function(employee){
self.detailedEmployee(employee);
}
<div data-bind="with: detailedEmployee">
Data to show
</div>
As you can see, your ViewModel don't know anything about how data should be shown. It knows only about data that should be shown. The with binding will display content only when detailedEmployee is defined. Next, we should find a binding similar to with but one that will display content in the popup. Let's give it the name modal. Its code is like this:
ko.bindingHandlers['modal'] = {
init: function(element) {
$(element).modal('init');
return ko.bindingHandlers['with'].init.apply(this, arguments);
},
update: function(element, valueAccessor) {
var value = ko.utils.unwrapObservable(valueAccessor());
var returnValue = ko.bindingHandlers['with'].update.apply(this, arguments);
if (value) {
$(element).modal('show');
} else {
$(element).modal('hide');
}
return returnValue;
}
};
As you can see, it uses the with plugin internally, and shows or hide a popup depending on value passed to binding. If it is defined - 'show'. If not - 'hide'. Its usage will be the as with:
<div data-bind="modal: detailedEmployee">
Data to show
</div>
The only thing you need to do is to use your favorite modals plugin. I prepared an example with the Twitter Bootstrap popup component: http://jsfiddle.net/euvNr/embedded/result/
In this example, custom binding is a bit more powerful; you could subscribe the onBeforeClose event and cancel this event if needed. Hope this helps.

The JSFiddle linked to in the answer provided by #Romanych didn't seem to work anymore.
So, I built my own example (based upon his original fiddle) with full CRUD support and basic validation using Bootstrap 3 and the Bootstrap Modal library: https://jsfiddle.net/BitWiseGuy/4u5egybp/
Custom Binding Handlers
ko.bindingHandlers['modal'] = {
init: function(element, valueAccessor, allBindingsAccessor) {
var allBindings = allBindingsAccessor();
var $element = $(element);
$element.addClass('hide modal');
if (allBindings.modalOptions && allBindings.modalOptions.beforeClose) {
$element.on('hide', function() {
var value = ko.utils.unwrapObservable(valueAccessor());
return allBindings.modalOptions.beforeClose(value);
});
}
},
update: function(element, valueAccessor) {
var value = ko.utils.unwrapObservable(valueAccessor());
if (value) {
$(element).removeClass('hide').modal('show');
} else {
$(element).modal('hide');
}
}
};
Example Usage
The View
<div data-bind="modal: UserBeingEdited" class="fade" role="dialog" tabindex="-1">
<form data-bind="submit: $root.SaveUser">
<div class="modal-header">
<a class="close" data-dismiss="modal">×</a>
<h3>User Details</h3>
</div>
<div class="modal-body">
<div class="form-group">
<label for="NameInput">Name</label>
<input type="text" class="form-control" id="NameInput" placeholder="User's name"
data-bind="value: UserBeingEdited() && UserBeingEdited().Name, valueUpdate: 'afterkeydown'">
</div>
<div class="form-group">
<label for="AgeInput">Age</label>
<input type="text" class="form-control" id="AgeInput" placeholder="User's age"
data-bind="value: UserBeingEdited() && UserBeingEdited().Age, valueUpdate: 'afterkeydown'">
</div>
<!-- ko if: ValidationErrors() && ValidationErrors().length > 0 -->
<div class="alert alert-danger" style="margin: 20px 0 0">
Please correct the following errors:
<ul data-bind="foreach: { data: ValidationErrors, as: 'errorMessage' }">
<li data-bind="text: errorMessage"></li>
</ul>
</div>
<!-- /ko -->
</div>
<div class="modal-footer">
<button type="button" data-dismiss="modal" class="btn btn-default">Cancel</button>
<button type="submit" class="btn btn-primary">Save Changes</button>
</div>
</form>
</div>
The ViewModel
/* ViewModel for the individual records in our collection. */
var User = function(name, age) {
var self = this;
self.Name = ko.observable(ko.utils.unwrapObservable(name));
self.Age = ko.observable(ko.utils.unwrapObservable(age));
}
/* The page's main ViewModel. */
var ViewModel = function() {
var self = this;
self.Users = ko.observableArray();
self.ValidationErrors = ko.observableArray([]);
// Logic to ensure that user being edited is in a valid state
self.ValidateUser = function(user) {
if (!user) {
return false;
}
var currentUser = ko.utils.unwrapObservable(user);
var currentName = ko.utils.unwrapObservable(currentUser.Name);
var currentAge = ko.utils.unwrapObservable(currentUser.Age);
self.ValidationErrors.removeAll(); // Clear out any previous errors
if (!currentName)
self.ValidationErrors.push("The user's name is required.");
if (!currentAge) {
self.ValidationErrors.push("Please enter the user's age.");
} else { // Just some arbitrary checks here...
if (Number(currentAge) == currentAge && currentAge % 1 === 0) { // is a whole number
if (currentAge < 2) {
self.ValidationErrors.push("The user's age must be 2 or greater.");
} else if (currentAge > 99) {
self.ValidationErrors.push("The user's age must be 99 or less.");
}
} else {
self.ValidationErrors.push("Please enter a valid whole number for the user's age.");
}
}
return self.ValidationErrors().length <= 0;
};
// The instance of the user currently being edited.
self.UserBeingEdited = ko.observable();
// Used to keep a reference back to the original user record being edited
self.OriginalUserInstance = ko.observable();
self.AddNewUser = function() {
// Load up a new user instance to be edited
self.UserBeingEdited(new User());
self.OriginalUserInstance(undefined);
};
self.EditUser = function(user) {
// Keep a copy of the original instance so we don't modify it's values in the editor
self.OriginalUserInstance(user);
// Copy the user data into a new instance for editing
self.UserBeingEdited(new User(user.Name, user.Age));
};
// Save the changes back to the original instance in the collection.
self.SaveUser = function() {
var updatedUser = ko.utils.unwrapObservable(self.UserBeingEdited);
if (!self.ValidateUser(updatedUser)) {
// Don't allow users to save users that aren't valid
return false;
}
var userName = ko.utils.unwrapObservable(updatedUser.Name);
var userAge = ko.utils.unwrapObservable(updatedUser.Age);
if (self.OriginalUserInstance() === undefined) {
// Adding a new user
self.Users.push(new User(userName, userAge));
} else {
// Updating an existing user
self.OriginalUserInstance().Name(userName);
self.OriginalUserInstance().Age(userAge);
}
// Clear out any reference to a user being edited
self.UserBeingEdited(undefined);
self.OriginalUserInstance(undefined);
}
// Remove the selected user from the collection
self.DeleteUser = function(user) {
if (!user) {
return falase;
}
var userName = ko.utils.unwrapObservable(ko.utils.unwrapObservable(user).Name);
// We could use another modal here to display a prettier dialog, but for the
// sake of simplicity, we're just using the browser's built-in functionality.
if (confirm('Are you sure that you want to delete ' + userName + '?')) {
// Find the index of the current user and remove them from the array
var index = self.Users.indexOf(user);
if (index > -1) {
self.Users.splice(index, 1);
}
}
};
}
Initializing Knockout with the View and the ViewModel
var viewModel = new ViewModel();
// Populate the ViewModel with some dummy data
for (var i = 1; i <= 10; i++) {
var letter = String.fromCharCode(i + 64);
var userName = 'User ' + letter;
var userAge = i * 2;
viewModel.Users.push(new User(userName, userAge));
}
// Let Knockout do its magic!
ko.applyBindings(viewModel);

I would create another observable that wraps the employee.
this.detailedEmployee = ko.observable({}),
var self = this;
this.showDetails = function(employee){
self.detailedEmployee(employee);
$("#dialog").dialog("show"); //or however your dialog works
}
Attach the click to showDetails. Then you can just call applyBindings on page load.