JS Practice — Built-in Objects

valueOf() — used in arithmetic

📖 Usage Example

const d = new Date('2024-01-15T00:00:00.000Z')
d.valueOf()  // → 1705276800000
d.valueOf() === d.getTime()  // → true

Use valueOf() to get the millisecond timestamp of a Date; it equals getTime() and is called automatically in arithmetic expressions.

Date.prototype.valueOf()

When you subtract two Dates, JavaScript calls valueOf() automatically, returning the difference in ms.

Challenge: Verify that subtracting two Dates gives a number (the difference in ms).

💡 Hints (1)

• Date subtraction implicitly calls valueOf() on both operands, yielding the ms difference