jQuery bind to keyup only, not focus

This seems like a simple thing but google hasn't turned up anything for me:

How can I bind to a text / value change event only, excluding an input gaining focus? Ie, given the following:

$(function(){
   $('input#target').on('keyup', function(){
     alert('Typed something in the input.');
   });
 });
 

...the alert would be triggered when the user tabs in and out of an element, whether they actually input text or not. How can you allow a user to keyboard navigate through the form without triggering the event unless they input/change the text in the text field?

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