I was inspired by this question on Stack Overflow: http://stackoverflow.com/questions/1224133/1224191.

Modifying a val() on a form element feels a bit kludgy. If val took a function as an argument (which gets the original value and returns the new one), we could do things like this:

From the SO question

$('#abc').val(function(v) { return v + "test"; });

More realistic example

var formatPhoneNumber = function (input) { ... };

...

$('.phone').val(formatPhoneNumber);

}