can someone please tell me this is a joke…

org.mozilla.javascript.EcmaError: TypeError: Cannot call method "toLowerCase" of undefined

.toLowerCase() is not supported in SuiteScript????????

.toLowerCase() definitely works. The above isn’t saying the function is undefined, it’s saying whatever you are trying to call it on is undefined. Are you sure you’re calling it on a string? Did you concatenate something? Rhino sometimes does weird things and you have to cast to a string.

You need check if your variable is not defined