JavaScript’s Date object provides a function for getting the milliseconds from the UNIX epoch - getTime():

var timeStamp = new Date().getTime();

However, there is a handy shortcut that gets the same thing:

var timeStamp = +new Date();

It makes me wonder if the +new shortcut can work for any other JavaScript object but I haven’t had a chance to look yet.

Update: Apparently it’s just the unary operator (http://xkr.us/articles/javascript/unary-add/). From the article:

The unary + operator, when used on types other than string, will internally attempt to call valueOf() or toString() (in that order) and then attempt to convert the result to a number. Thusly, the unary + operator can successfully convert many of the native JS types with certain restrictions.