Cannot call method toUpperCase of undefined

Question

if (json.ScheduleCareProviderScheduledPatientsGetResult.Appointments[i].Patient.Firstname.toUpperCase().indexOf(searchBarValue.toUpperCase()) == 0) {

为什么我会收到此错误。

Answer 1

Because

json.ScheduleCareProviderScheduledPatientsGetResult.Appointments[i].Patient.Firstname

is undefined.

Answer 2

Either json.ScheduleCareProviderScheduledPatientsGetResult.Appointments[i].Patient.Firstname or searchBarValue are undefined. Make sure they're not null before you call this line!