JS Practice — Built-in Objects

Number.isNaN() — undefined returns false, unlike global isNaN

📖 Usage Example

// Check for NaN without coercion
Number.isNaN(NaN)    // → true
Number.isNaN('NaN')  // → false (no coercion)
Number.isNaN(42)     // → false

Use Number.isNaN() instead of the global isNaN() to check for NaN without coercing the argument first.

Number.isNaN() — undefined

isNaN(undefined) returns true (coerces to NaN). Number.isNaN(undefined) returns false.

💡 Hints (1)