Javascript + operator

Question

What is the application of the plus operator in these cases? I have seen it used in these ways but don't see how it operates.

start = +new Date;

+array[i]

+f.call(array, array[i], i)

x = +y

One more: http://stackoverflow.com/questions/8330499/operator-before-expression-in-javascript-what-does-it-do — bfavaretto, May 17 '13 at 20:27

jAndy · Accepted Answer · 2013-05-17T20:30:38.583

10

+ will implicitly cast a string / boolean value into a Number().

+"66" === 66

If the string cannot be converted into a Number, the value will be NaN

+"not possible" // evaluates to NaN

In the case of a Date() object, + will also cast the data into its numerical representation, that is the UNIX timestamp.

So, finally spoken, leading an expression with + is pretty much the same as explicitly wrapping the Number() constructor around it:

+new Date()

equals

Number( new Date() )

edited May 17 '13 at 20:30

answered May 17 '13 at 20:24

jAndy

or any primitive value into a number for that matter... – dandavis May 17 '13 at 20:25

1 Answers1