Knockout is a JavaScript library that helps you to create responsive display(UI) It is based on Model–view–viewmodel (MVVM) pattern It provides a simple two-way data binding mechanism between your data model and UI It was developed and is maintained as an open source project by Steve Sanderson, a Microsoft employee on July 5, 2010

1. Introduction to Knockout JsIntroduction to Knockout Js
Teena Vashist
Software Consultant
Knoldus Software LLP
Teena Vashist
Software Consultant
Knoldus Software LLP

2. AGENDAAGENDA
What is knockout js
MVVM
Features
Why knockout js
Observable
Controlling dependency tracking
Bindings
Demo
What is knockout js
MVVM
Features
Why knockout js
Observable
Controlling dependency tracking
Bindings
Demo

3. What is Knockout Js
● Knockout is a JavaScript library that helps you to create
responsive display(UI)
● It is based on Model–view–viewmodel (MVVM) pattern
● It provides a simple two-way data binding mechanism
between your data model and UI
● It was developed and is maintained as an open source project
by Steve Sanderson, a Microsoft employee on July 5, 2010

4. MVVM Design Pattern
MVVM pattern has 3 key parts:
● Model – It stores application data and is independent of any
UI
● View – It provides User Interface
● View-Model – It connect model and view and a pure-code
representation of the data and operations on a UI

5. MVVM

6. Features
● Declarative Bindings
It allows you to connect your UI element to your data model
● Automatic UI Refresh
When your data model's state changes, your UI updates automatically
● Dependency Tracking
Implicitly set up chains of relationships between model data, to transform and combine it
● Extensible
This implements custom behaviors as new declarative bindings for easy reuse in just a few lines
of code. Knockout is also flexible to integrate with other libraries and technologies

7. Why Knockout Js ?
● Small & lightweight - 54kb minified
● Compatible with other technologies
● Open source and free
● Smart feature - self updating UI
● Fully documented
● It supports all mainstream browsers:
IE 6+, Firefox 2+, Chrome, Safari, others

8. To create a view model with KO
Just declare any JavaScript object, For example
var employeeViewModel = {
empName: 'Teena',
empId: '12'
};
ViewModel holds
the UI's
underlying data
and behaviors

9. ViewModel inside a View
You can then create a very simple view of this view model
using a declarative binding.
Name is <span data-bind="text: empName"></span>
Binding attribute
DOM element with model
properties

10. Activating Knockout Js
ko.applyBindings(employeeViewModel);
Here, view will display like you would have written following
html
Name is <span>Teena</span>
Activate Knockout

11. Observables
These are special JavaScript objects that can notify subscribers about
changes, and can automatically detect dependencies.
Rewrite the preceding view model object as follows:
var employeeViewModel = {
empName: ko.observable('abc'),
empId: ko.observable(49)
};

12. Read/Write Properties of Observable
● To read: employeeViewModel.empName()
● To write: employeeViewModel.empName('Teena')
● To write value to multiple observable:
employeeViewModel.empName('bob').empId('15')

13. Computed Observable
Computed observable are functions that are dependent on one or more other
observables and will automatically update whenever any of these dependencies
change.
var empDetail =
ko.computed(function() {
return employeeViewModel.empName() +
" employee id: " + employeeViewModel.empId();
});

14. Controlling Dependencies
● Knockout’s automatic dependency tracking. But we might sometimes need to
control which observables will update your computed observable.
var empDetail =
ko.computed(function() {
return employeeViewModel.empName() +
" employee id: " +
employeeViewModel.empId.peek();
});

15. Knockout Bindings
● Controlling text and appearance:
visible, text, html, css, style, attr
● Control flow:
foreach, if, ifnot, with ,component
● Working with form fields:
click, event, submit, enable, disable, value, textInput etc.

16. Demo
https://github.com/knoldus/play-knockout-demo

17. Questions ?

18. References
● http://knockoutjs.com/
● http://www.knockmeout.net/
● https://msdn.microsoft.com/