Smashing Node.js: JavaScript Everywhere, 2nd Edition

Chapter 10: WebSocket

So far, most website and web application developers are accustomed to communicating exclusively with a server by making HTTP requests that are followed by HTTP responses.

The model of requesting a resource by specifying its URL, Content-Type, and other attributes that you saw in previous chapters works well if you keep in mind the use case that the World Wide Web was crafted to solve. The web was created to deliver documents that were heavily interlinked to each other. URLs have paths because documents typically have hierarchies in file systems. And each level of hierarchy can contain indexes with hyperlinks.

Consider the following, for example:

GET /animals/index.html

GET /animals/mammals/index.html

GET /animals/mammals/ferrets.html

With time, however, the web became more and more interactive. The traditional web that was about retrieving entire documents every time the user clicked is less common nowadays, especially with all the tools that HTML5 makes available. You can now create very sophisticated web applications that often have completely deprecated desktop application counterparts, games, text editors, and more.

AJAX

The Web 2.0 marked the uprise of the web application. One of its key ingredients was AJAX, which translated into a snappier user experience for a fundamental reason: you no longer had to retrieve an entire HTML document every time the user interacted with the server.

For example, if you are updating your profile on a social networking ...