Symptoms
DOM manipulation statements in onLoad client scripts fails after listV3 is enabled.
Release
All releases
Cause
ListV3 DOM is different than the listV2.
Resolution
DOM manipulation is not advised by serviceNow as it causes issues such as these.
Refer : AvoidDOMManipulation
We can wrap the DOM manipulation commands such as these in addAfterPageLoadedEvent in the onLoad client script as below.
function onLoad() {
addAfterPageLoadedEvent(function(){
document.getElementById('lookup.incident.u_business_service').style.display = "none";
});
//Your rest of the onload script
}