User object properties and their types: user.id: 1 (number) user.name: Alice (string) user.email: alice@example.com (string) user.active: true (boolean) Using string methods on name property: Uppercase: ALICE Length: 5 Nested object properties: user.details.age: 30 (number) user.details.address.city: New York (string) user.details.address.country: USA (string) Using methods on nested properties: Age (fixed decimal): 30 City (lowercase): new york In TypeScript, accessing non-existent properties would cause compile-time errors: user.age // Error: Property 'age' does not exist user.details.name // Error: Property 'name' does not exist user.details.address.zip // Error: Property 'zip' does not exist