Q26. What is the difference between optional and nullable properties?
An optional property may be absent. A nullable property explicitly allows null in its value type. With strict null checking, these are distinct concepts: name?: string and name: string | null express different contracts.
An API may omit an optional field entirely, while a required nullable field must exist but may contain null.
Note
Interview approach: define the concept, explain why it matters, then mention one trade-off or limitation.
TypeScript concept
// Illustrative TypeScript contract
type Identifier = string;
const id: Identifier = "item-1";💡 The example demonstrates the compile-time contract discussed in this question.
Key Takeaways
- Explain the concept in your own words.
- Know the practical trade-off and its limits.
- Use a small example to demonstrate the idea.
Knowledge Check
Which type requires the property to exist but permits null?