Book Image

KnockoutJS by Example

By : Adnan Jaswal
Book Image

KnockoutJS by Example

By: Adnan Jaswal

Overview of this book

KnockoutJS By Example is a project-based guide that introduces the key features and concepts of knockout.js. It helps you create an application skeleton and a Hello World application. You will develop a To-Do list application that aims to show the basic features of knockout.js in action, such as data binding and observables, following which you will develop a dynamic online customer registration form that captures and validates customer information. This book will further walk you through developing a customer banking portal, which demonstrates the use of knockout.js with components such as navigation bars, tabs, carousels, master details view, panels, forms, and wizards. You will also discover how to use token-based authentication and authorization to secure the customer banking portal, and move on to creating an editable products grid with CRUD operations. Finally, you will explore how to use the Google Maps API with knockout.js. KnockoutJS By Example will not only leave you with a basic understanding of knockout.js fundamentals but also take you through some of the advanced features. It will help you get a web application up and ready instantly.
Table of Contents (17 chapters)
KnockoutJS by Example
Credits
About the Author
Acknowledgment
About the Reviewers
www.PacktPub.com
Preface
Index

Handling the authentication error


This user story is about displaying a message to the user if the login fails based on the username and password that the user has provided. To implement this user story, we will take the following steps:

  • Add a flag to the authenticator module to show or hide the authentication error

  • Modify the login method of the authenticator module to check for the authentication error

  • Update the view to add an alert box with the authentication error

Let's get started by opening the authenticator module and adding an observable that will serve as a flag to show or hide the authentication error alert box:

/* flag to show authentication failed message */
var showAuthenticationFailed = ko.observable(false);

Add the preceding flag to the return statement of the authenticator module. Now modify the login method to check whether the server returns a false for the login call. In case of authentication failure, set the showAuthenticationFailed flag to false and do not proceed any further...