chapter.checkpoint
Modeling Real Application Data
Pause here and make sure the main ideas feel clear before moving to the next chapter.
Review recommended
What you should understand now
Use object types, unions, narrowing, and generics to model changing application states.
Object types and interfaces
Give structured data a clear contract.
Unions and narrowing
Represent several allowed states and safely discover the current one.
Generics and reusable constraints
Preserve type information across reusable functions.
progress.review
Chapter progress
Lessons completed
0/3
0% complete
Exercises attempted
0/3
0% complete
Quizzes passed
0/1
0% complete
Before you move on
Use this quick review if anything still feels unclear.
Review chapterRetake chapter quiz
Complete the lessons, pass the exercises, and pass the quiz to unlock the next chapter.