What's faster to parse lots of data (5Mb): eval or json?

Question

I want to get, via ajax, a collection of data objects and parse them into JS data.

Currently I have 2 choices: - Server returns valid javascript code and then I eval it. - Server returns JSON object and then I eval the json object

What is the fastest of these in Firefox? (I only care about the "parsing" performance, not server or data transfer)

Answer 1

In Firefox 3.5+ there is a native json parsing function window.JSON.parse - this would likely be the fastest. In older browsers, you might have better luck with (new Function("return "+json))()

Answer 2

Have a look at the results VinylFox came up with when he tested JSON decoding in the wild. The native functions performed best across all browsers.