Book Image

HTML5 Data and Services Cookbook

Book Image

HTML5 Data and Services Cookbook

Overview of this book

HTML5 is everywhere. From PCs to tablets to smartphones and even TVs, the web is the most ubiquitous application platform and information medium bar. Its becoming a first class citizen in established operating systems such as Microsoft Windows 8 as well as the primary platform of new operating systems such as Google Chrome OS. "HTML5 Data and Services Cookbook" contains over 100 recipes explaining how to utilize modern features and techniques when building websites or web applications. This book will help you to explore the full power of HTML5 - from number rounding to advanced graphics to real-time data binding. "HTML5 Data and Services Cookbook" starts with the display of text and related data. Then you will be guided through graphs and animated visualizations followed by input and input controls. Data serialization, validation and communication with the server as well as modern frameworks with advanced features like automatic data binding and server communication will also be covered in detail.This book covers a fast track into new libraries and features that are part of HTML5!
Table of Contents (21 chapters)
HTML5 Data and Services Cookbook
About the Authors
About the Reviewers

Using asynchronous server-side validation

Many validation checks can only be performed at the server side. The following are the examples:

  • When validating a user registration form, we need to check if the entered username is available

  • When the user enters a postal address, we might need to ask an external service to verify if the address is correct

The problem with server-side validation checks is that they need to be asynchronous. As a result, they cannot be written in JavaScript as functions that return validation results.

To solve this problem, in this recipe we're going to make a validator that uses the continuation-passing style. The example has a username input field that is validated against the server. The server checks if the username is available for registration or already occupied by another user.

Getting ready

We're going to briefly look at the continuation-passing style. It's a style used by most of the JavaScript libraries for asynchronous operations, for example, server communication...