jQuery callback - strict violation

I get the basic idea about this not being in a method when in strict mode outlined here, but it gets a bit erudite, to be honest. So, in more prosaic terms:

I have a handler like so:

$('.myClass').one('keyup', function() {
    var $this = $(this);
    etc etc
});

I want to change it to this:

function myFunction () {
    var $this = $(this);
    etc etc
};
$('.myClass1').one('keyup', myFunction);
$('.myClass2').one('keyup', myFunction); etc

It doesn't like it because in strict mode because I'm using this outside of a method. I get that.

However, I need to have myFunction separate to the handler, because (1) it's attached to various classes/elements and (2) I am using .off().one('keyup', myFunction) to reset the one handler for various classes at various points.

So how do I get around having a separate callback function without violating the this business?