Is the return value +new Date() different from Date.now()?

Question

Assuming I have two functions

function newDate(){
  return +new Date();
}
function dateNow(){
  return Date.now();
}

So I wonder if it makes a difference that one returns +new Date() and another Date.now()?

In your title and your post you wrote `+new Date()` did you mean this or did you mean `new Date()` without the `+` sign? — surfmuggle, May 12 '16 at 21:52

score 2 · Answer 1 · edited May 15 '16 at 06:32

According to the spec:

15.9.4.4 Date.now ( )
The now function return a Number value that is the time value designating the UTC date and time of the occurrence of the call to now.

15.9.3.3 new Date ( )
The [[PrimitiveValue]] internal property of the newly constructed object is set to the time value (UTC) identifying the current time.

Coercing the Date object created by new Date() to a number with the unary + operator results in the primitive value. So the question of whether your two cases are always the same boils down to whether the two things below are identical:

date and time of the occurrence of the call to now
the time value identifying the current time

It would seem to be a good bet that they are.

3rd party edit

The chrome (v49) console returns this:

x = Date.now(), y1 = +new Date(), y2 = new Date();
x returns 1463201841680
y1 returns 1463201841680
y2 returns Sat May 14 2016 06:57:21 GMT+0200

score 1 · Answer 2 · edited May 23 '17 at 12:00

1

They give the same value. Verified in chrome devtools console

Date.now() === +new Date()
> true

However, performance is a little better with Date.now()

Performance - Date.now() vs Date.getTime()

edited May 23 '17 at 12:00

Community

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answered May 12 '16 at 20:22

Anthony Chung

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**Date.now()** return the **timestamp** or not ? – c2080584 May 12 '16 at 21:06
it does return a timestamp. Please mark as complete if you agree – Anthony Chung May 12 '16 at 21:07
ok. will **+new Date()** returns the numeric equivalent of the date or not ? – c2080584 May 12 '16 at 21:12
my answer indicates that they are numerical equivalents – Anthony Chung May 12 '16 at 21:20
In my chrome 49 this `Date.now() === new Date();` returns false and this `Date.now() === +new Date();` returns true. – surfmuggle May 12 '16 at 21:54

Is the return value +new Date() different from Date.now()?

2 Answers2

3rd party edit