JS Practice — Built-in Objects

toJSON() — epoch returns ISO string

📖 Usage Example

const d = new Date('2024-01-15T00:00:00.000Z')
d.toJSON()  // → '2024-01-15T00:00:00.000Z'
JSON.stringify({ date: d })  // uses toJSON()

Use toJSON() to get the ISO 8601 UTC string representation of a Date; it is called automatically by JSON.stringify.

Date.prototype.toJSON()

Returns the same ISO 8601 string as toISOString(). Useful for JSON serialization.

Challenge: Verify that new Date(0).toJSON() returns '1970-01-01T00:00:00.000Z'.

💡 Hints (1)

• toJSON() calls toISOString() internally — they produce the same output for valid dates