有点像OOP里面extract method的意思,比如一片代码总是重复出现，你可能就需要抽象出一个单独的方法来封装这片重复的代码.
在事件委托中，子元素的事件委托给容器元素，从而避免为每个子元素添加事件handle，增加重复代码。
Use relative URLs
/index.html instead of http://www.example.com/index.html
Table 9-3. Relative equivalents of http://www.example.com/path/page.html
Fully specified destination URL Relative equivalent
http://subdomain.example.com/ //subdomain.example.com
http://www.example.com/path/page2.html page2.html
http://www.example.com/index.html /index.html
http://www.example.com/path2/page.html ../path2/page.html
http://www.example.com/path/page.html#f=bar #f=bar
http://www.example.com/path/page.html?q=foo ?q=foo
Strip whitespace
YUI Compressor: CSS http://developer.yahoo.com/yui/compressor/
ShrinkSafe: http://shrinksafe.dojotoolkit.org/
JSMin: http://www.crockford.com/javascript/jsmin.html