Practical chapter 02 · guided challenge · 4 test cases per challenge
Safe nested data
Distinguish missing members, null, and invalid content before an expression uses a value.
01Usable email addressCheck presence, null, and an empty string in the correct order.Solve challenge02Country in a shipping addressMove safely through three levels of nested data.Solve challenge03Exactly one contact methodRequire an email or a phone number, but not both.Solve challenge04Notification channelSelect a preferred channel, a safe fallback, or none.Solve challenge