Thanks Paul for the resource link, however that's not quite the information I was looking for. I'm aware of how to trigger an onChange event. What I'm looking for is something similar to lasersfiche's lookupcomplete event which can be used to run a function when a specific lookup rule has completed, but instead of lookup rules I'm interested on pre-filling of fields from query parameters.  

For example when a routing number is pre-filled I'd like to automatically trigger an api call to fetch some data about the associated bank. When I try to simply trigger a change event it will not actually pick up the prefilled data, but when I wrap it in a setTimeout it will work as expected. My suspicion is that the prefilling is occurring after the 

$(document).ready()

I hope that help clarify my question.