JS Practice — Built-in Objects

valueOf() — implicit conversion in arithmetic

📖 Usage Example

// Retrieve the primitive value of an object
const n = new Number(42)
n.valueOf()   // → 42
const obj = { valueOf() { return 10 } }
obj + 5       // → 15

Use valueOf() to retrieve the underlying primitive value of an object; JavaScript calls it automatically in numeric contexts.

valueOf() — implicit type coercion

When an object is used in arithmetic (like +, -, *), JavaScript automatically calls valueOf() to convert it to a primitive. You can leverage this by overriding valueOf().

Challenge: Show how a custom valueOf is implicitly called in arithmetic.

💡 Hints (1)

• JavaScript uses valueOf for type coercion in arithmetic and comparison contexts