JSON and XML
JSONJSON, short for JavaScript Object Notation, is an open standard, lightweight, text-based, human-readable data interchange format derived from the JavaScript programming language for representing simple data structures and associative arrays (called objects). Despite its close connection to JavaScript, it is language-independent, with parsers available for virtually every programming language in existence.
The JSON format is often used for serializing and transmitting structured data between a server and web application, serving as an alternative to XML.
Many browsers now support native JSON, which is generally faster.
JSON vs XML
http://stackoverflow.com/questions/1579269/any-particular-advantage-to-using-json-over-xml-with-flash
http://stackoverflow.com/questions/584985/what-are-the-advantages-and-disadvantages-of-json-vs-xml-for-ajax-requests
Advantages of JSON
1. JSON is typically a more efficient data encoding method than XML; it’s much smaller than XML. XML is verbose, and cumbersome, 90% hypertext and 10% data. JSON can save bandwidth and get much better response times, excellent for AJAX.
2. JSON can be parsed more efficiently, it is a subset of JavaScript, we can easily parse it in JavaScript, such as call eval.
Advantages of XML
XML has been around for quite a while, and has lots of tool support.
XML has schema, we can use schema to validate the data.
Disadvantages
Using XML in JavaScript is quite verbose and cumbersome.
JSONP
JSONP or "JSON with padding" is a complement to the base JSON data format, a usage pattern that allows a page to request and more meaningfully use JSON from a server other than the primary server.
HTML <script> tags can retrieve data from other sites.
<script type="text/javascript" src="http://domain1.com/getjson?jsonp=parseResponse"></script>
The server wraps its JSON response with this prefix, or "padding", before sending it to the browser. When the browser receives the wrapped response from the server it is now a script, rather than simply a data declaration.
Same origin policy
The policy permits scripts running on pages originating from the same site to access each other's methods and properties with no specific restrictions, but prevents access to most methods and properties across pages on different sites.
