JS Practice — Built-in Objects

Type Guard — isNullOrUndefined

📖 Usage Example

function isNullOrUndefined(x: unknown): x is null | undefined {
  return x === null || x === undefined
}
isNullOrUndefined(null)   // → true
isNullOrUndefined(0)      // → false

Check x === null || x === undefined to detect both nullish values precisely.

Type Guards: isNullOrUndefined

Challenge: Implement isNullOrUndefined(x: unknown): x is null | undefined.

isNullOrUndefined(null)      // → true
isNullOrUndefined(undefined) // → true
isNullOrUndefined(0)         // → false

💡 Hints (1)

• Use strict equality (===) with both null and undefined.