jquery 1.5 ajax的改善

jquery 1.5 ajax的改进
源文见: http://api.jquery.com/extending-ajax/

相比之前的版本, 重写了ajax模块, 引入更多的扩展点. 三个概念:
Prefilters
A prefilter is a callback function that is called before each request is sent, and prior to any $.ajax() option handling.
Prefilters are registered using $.ajaxPrefilter(), and a typical registration looks like this:

Handling Custom Data Types
在jquery源码里, 已定义了几种处理类型
The jQuery Ajax implementation comes with a set of standard dataTypes, such as text, json, xml, and html.

Use the converters option in $.ajaxSetup() to augment or modify the data type conversion strategies used by $.ajax().

The unminified jQuery source itself includes a list of default converters, which effectively illustrates how they can be used: 



When you specify a converters option globally in $.ajaxSetup() or per call in $.ajax(), the object will map onto the default converters, overwriting those you specify and leaving the others intact.

For example, the jQuery source uses $.ajaxSetup() to add a converter for "text script":
jQuery.ajaxSetup({  accepts: {    script: "text/javascript, application/javascript"  },  contents: {    script: /javascript/  },  converters: {    "text script": jQuery.globalEval  }});