Javascript and ajax not displaying autmatic filled values (only on IE8)

Javascript and ajax not displaying autmatic filled values (only on IE8)

Hello everyone,

I have 2 fields (representing iban account and bic code). When I fill the iban, I want the bic to be filled automatically. I use a small scrip doing it and it works well. Unfortunately, it doesn't work for IE8 (it works for Chrome, Firefox, IE11). Here is my script : 

  1. <label for="test">BIC</label><input id="whatever" type="text" name="testWhatever" value="" class="ajax up" maxlength="11" onchange="getAjaxLabel(this,'updtComp','warning',null,true);" size="20" /><span class="mandatory">&nbsp;</span></p>...

The field is filled thx to "getAjaxLabel()".
Do you have any idea why it doesn't work for IE8 ? (or what settings could I tune to make this browser works).

Thanks a lot ! 

Best regards.