Iulian Dogariu

JSON is an informal standard for describing structured data. It is human-readable, less verbose than XML, and has a distinct advantage which I’ll mention later.

Short example: say you want to define an address book entry. In JSON it might look like this:

Compare the verbosity of the above to the equivalent XML here:

Using JSON, you can nest arbitrarily structured data, making use of maps (comma-separated lists of forms like ‘key’: ‘value’, surrounded by braces) and sequences (comma-separated values, surrounded by brackets).

You can use JSON in lots of places, even in those where the more “enterprisey” developers would use XML; like, say, to write config files.

However there is a particular affinity between JSON and the AJAX techniques. While doing AJAX you’ll often find the need to fetch some data from the server and parse it. Guess what: in JavaScript you don’t need a parser to parse JSON, because JSON syntax is JavaScript syntax. In other words, you parse it by calling eval().
JSON after all stands for ‘JavaScript Object Notation’

And, as you probably guessed, generating JSON is a breeze. Here’s a quick’n'dirty function written in the Groovy programming language, that serializes a construct of Java maps and lists into JSON: