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any (vs unknown)
6 exercises
any turns off type checking completely. It spreads quickly through your code and hides bugs. Prefer unknown when you don't know a type yet:
// ❌ Dangerous - no checks
function process(data: any) {
return data.value.toUpperCase(); // Might crash!
}
// ✅ Safe - forces checks
function process(data: unknown) {
if (typeof data === "object" && data !== null && "value" in data) {
const obj = data as { value: string };
return obj.value.toUpperCase();
}
}unknown forces you to check a value before using it, making your code safer.
Narrowing techniques:
typeoffor primitives –typeof x === 'string'Array.isArray()for arraysinoperator for properties –'name' in obj- Custom type guards –
function isUser(x: unknown): x is User
In this category, you'll:
- Use
unknownfor inputs you need to validate - Narrow safely with runtime checks
- Parse JSON and validate structures
- Avoid leaking
anyinto your code - Migrate gradually from
anytounknown
By the end, you'll understand why unknown is safer than any and how to work with it confidently.