First make sure you have the 'Pass execution context as first parameter' checkbox ticked when attaching the onSave Event Handler
In the ValidateData method make sure you have a parameter defined to receive the Execution Object.
function ValidateData(ExecutionObj){
//Place all your data validation here
//In case data is not valid call the below method
// The getEventArgs() method returns an object with methods to manage the Save event.
// The preventDefault() method cancels the save operation
ExecutionObj.getEventArgs().preventDefault();
}
function ValidateData(ExecutionObj){
//Place all your data validation here
//In case data is not valid call the below method
// The getEventArgs() method returns an object with methods to manage the Save event.
// The preventDefault() method cancels the save operation
ExecutionObj.getEventArgs().preventDefault();
}
Refer this link for more details ...
