JS Practice — Built-in Objects

Type Guard — isNonEmptyString

📖 Usage Example

function isNonEmptyString(x: unknown): x is string {
  return typeof x === 'string' && x.length > 0
}
isNonEmptyString('')        // → false
isNonEmptyString('hello')   // → true

Layering value-level constraints onto typeof checks creates more specific type guards.

Type Guards: Refined String Guard

Challenge: Implement isNonEmptyString(x: unknown): x is string — true only for non-empty strings.

isNonEmptyString('hello')  // → true
isNonEmptyString('')       // → false
isNonEmptyString(null)     // → false

💡 Hints (1)

• Check typeof and length > 0.