Backbone.js需要json2.js吗？

Question

From the site:

Backbone's only hard dependency is either Underscore.js ( > 1.4.3) or Lo-Dash. For RESTful persistence, history support via Backbone.Router and DOM manipulation with Backbone.View, include json2.js, and either jQuery ( > 1.4.2) or Zepto.

Why is json2.js mentioned? I have run my app in ie7-9 among other browsers without requiring this file and it works. Is this a performance thing?

Answer 1

json2.js provides JSON.parse and JSON.stringify functions, which Backbone depends on. They've been included in browsers for a while but it's probably listed in case your environment doesn't include it, or you want a consistent implementation in your app.

Answer 2

That script adds JSON functionality to older browsers that will look just like native functionality that exists in newer browsers

https://github.com/douglascrockford/JSON-js

Answer 3

As the other answers have suggested, you only need to download and include the "manual" JSON library if you need to support older browsers; otherwise your browser will have it built in (which is how you saw Backbone work without issue).

For the exact list of which browsers have/don't have JSON built in, see: http://caniuse.com/#feat=json