what is the role of the plus sign(+) in the following function which is excerpt from jquery source code

Question

function now(){
    return +new Date;
}

questions :

what does the plus sign mean?
when can you create a new object with a constructor function but without the following parentheses, such as new Date but not new Date()

great thanks!

1. see http://stackoverflow.com/questions/221539/what-does-the-plus-sign-do-in-return-new-date — harto, Jul 08 '09 at 07:00

score 8 · Accepted Answer · answered Jul 08 '09 at 06:59

8

1 . The plus sign is the unary + operator.

That expression is equivalent to cast the Date object to number:

function now(){
    return Number(new Date);
}

2 . If you don't add the parenthesis, the new operator will call the object type (Date) parameterlessly

answered Jul 08 '09 at 06:59

1

... and converting a `Date` into a `Number` (any way you do it) is, basically, just a less readable way of invoking `getTime()`: https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Global_Objects/Date/getTime – gustafc Jul 08 '09 at 07:25

score 3 · Answer 2 · answered Jul 08 '09 at 07:11

3

Using the plus sign will convert the date into a number (the number of milliseconds since 1 Jan 1970)
You can do this whenever there are no parameters - although you may wish to include them still for readability.

answered Jul 08 '09 at 07:11

Fenton

2 Answers2