Professional JavaScript for Web Developers, 4th Edition

24Network Requests and Remote Resources

WHAT'S IN THIS CHAPTER?

• Using the XMLHttpRequest object
• Working with XMLHttpRequest events
• Cross-domain Ajax restrictions
• Fetch API
• Streams API

WROX.COM DOWNLOADS FOR THIS CHAPTER

Please note that all the code examples for this chapter are available as a part of this chapter’s code download on the book’s website at www.wrox.com/go/projavascript4e on the Download Code tab.

In 2005, Jesse James Garrett penned an online article titled “Ajax: A New Approach to Web Applications”. This article outlined a technique that he referred to as Ajax, short for Asynchronous JavaScript+XML. The technique consisted of making server requests for additional data without unloading the web page, resulting in a better user experience. Garrett explained how this technique could be used to change the traditional click-and-wait paradigm that the web had been stuck in since its inception.

The key technology pushing Ajax forward was the XMLHttpRequest (XHR) object, first invented by Microsoft and then duplicated by other browser vendors. Prior to the introduction of XHR, Ajax-style communication had to be accomplished through a number of hacks, mostly using hidden frames or iframes. XHR introduced a streamlined interface for making server requests and evaluating the responses. This allowed for asynchronous retrieval of additional information from the server, meaning that a user click didn't have to refresh the page to retrieve more data. Instead, an XHR object ...