如何格式化"12345"为"12,345"

拷贝自：
http://svn.globalize-rails.org/svn/globalize/trunk/lib/globalize/localization/core_ext.rb

javascript:

string.replace(/(\d)(?=(\d\d\d)+(?!\d))/g, function(s){return s+","})

ruby:

string.gsub(/(\d)(?=(\d\d\d)+(?!\d))/) { |match| match + ',' }