JavaScript Cookbook

Chapter 19. Working with Structured Data

19.0. Introduction

Even though it’s primarily a client-side development tool, JavaScript has access to several very sophisticated techniques and mechanisms for working with structured data.

Originally, most complex data management, particularly in relation to Ajax calls, was based either in HTML fragments or XML. HTML fragments are still popular. When returned from an Ajax request, the HTML formatted string can be used with innerHTML in order to easily append the HTML into the page. Of course, you have to trust the data you receive, and you can’t manipulate it until you actually insert the data into the page. Either that, or use various String functions to parse pieces out of the HTML string.

Data returned as XML is a richer option, because you can use the string to create a separate document object, from which you can access individual elements, just like you query the web page document now.

XML data is still widely supported, but another structure has gained a great deal of popularity: JavaScript Object Notation, or JSON. It’s so popular that JSON has been added to the most recent version of JavaScript, ECMAScript 5. JSON provides the richness of XML but without the performance hit client-side processing of XML can add.

JSON is basically the string serialization of JavaScript objects. Before ECMAScript 5, you had to use the eval function to convert the string to an object . Unfortunately, using the eval function on an unknown string is an application-security ...