Is there any difference between $(\".selector\").size() and $(\".selector\").length ?
They will both give you the same result but .length is slightly faster.
See http://api.jquery.com/size/:
The .length property is a slightly faster way to get this information.
No. size() returns length. By using length you only avoid one extra method call.
Length returns the same thing and is slightly faster according to the jQuery documentation.
Source: http://api.jquery.com/size/