The valueOf() method of Date instances returns the number of milliseconds for this date since the epoch, which is defined as the midnight at the beginning of January 1, 1970, UTC.
Syntax
valueOf()
Parameters
None.
Return value
A number representing the timestamp, in milliseconds, of this date. Returns NaN if the date is invalid.
Description
The valueOf() method is part of the type coercion protocol. Because Date has a [@@toPrimitive]() method, that method always takes priority over valueOf() when a Date object is implicitly coerced to a number. However, Date.prototype[@@toPrimitive]() still calls this.valueOf() internally.
The Date object overrides the valueOf() method of Object. Date.prototype.valueOf() returns the timestamp of the date, which is functionally equivalent to the Date.prototype.getTime method.
Examples
Using valueOf()
const d = new Date(0); // 1970-01-01T00:00:00.000Z
console.log(d.valueOf()); // 0