Change image base on input value

[davelf]

Link example: http://davejob.com/increment/test.html

I try to combine javascript increment in my input text to call some specific image, but it failed.

ex.
if value == 1, show image 1
if value == 2, show image 2
and so on..

i use .keyup and switch case function, but it only work when i type in the input box. If i click on the plus/ min button even the value change, the image don't.
Any suggestion for this problem, thanks