JavaScript Cookbook

Chapter 18. Communication

18.0. Introduction

This book has explored a lot of subjects, but the functionality that revolutionized web client development is (arguably) Ajax. With Ajax, we’re no longer dependent on the slow, cumbersome round-trips and associated page load times that plagued early websites. Now we can make an Ajax call, get some data, update the page—sometimes without the user even being aware that the activity is happening.

Ajax is also a relatively uncomplicated functionality, at least compared to other JavaScript functionality I’ve covered in the book. The main steps to an Ajax application are:

• Prepare the server-side API call.

• Make the call.

• Process the result.

Of course, there are interesting challenges that can occur at any time during these three steps, but for a basic application, it really is just that simple.

Ajax is now joined by a new communication kid: the postMessage. This new functionality originated with HTML5, though it has since split off to its own specification. It’s an uncomplicated functionality that allows for easy communication between a parent and child window, even if the child window is located in another domain.

Note

There are two other new communication APIs in work: Cross Origin Resource Sharing (CORS) and the Web Sockets API. Both are being developed in the W3C, and both are currently in Working Draft state: CORS at http://www.w3.org/TR/access-control/ and Web Sockets at http://dev.w3.org/html5/websockets/.

CORS is a way of doing cross-domain Ajax ...