JS Practice — Built-in Objects

Number.NaN — Number.isNaN vs global isNaN

📖 Usage Example

// Represents Not-a-Number
Number.NaN        // → NaN
Number.isNaN(Number.NaN)  // → true
Number.NaN === Number.NaN // → false (NaN is never equal to itself)

Use Number.NaN as a named constant for Not-a-Number; always check for it with Number.isNaN() since NaN !== NaN.

Number.isNaN vs global isNaN

Number.isNaN() does NOT coerce its argument, while global isNaN() does.

isNaN('hello')        // → true  (coerces 'hello' → NaN first)
Number.isNaN('hello') // → false (no coercion)

💡 Hints (1)

• Prefer `Number.isNaN()` in modern code to avoid unexpected coercion.