what is use of ~~ in javascript?

Question

Possible Duplicate:
Understanding javascript bitwise NOT

I found it here: front-end-interview-questions question down below. what this code ~~3.14 will return?

I searched on google but didn't found anything on this.

Or [Javascript Tilde & Two's complement](http://stackoverflow.com/questions/12337360/javascript-tilde-twos-complement) — verdesmarald, Sep 26 '12 at 06:07
**Simple answer**: fastest trimming decimals operation (as fast as bitwise OR) `~~3.14` is the same as `3.14 | 0` — Robert Koritnik, Mar 05 '13 at 08:20

score 5 · Answer 1 · edited Sep 26 '12 at 06:08

5

It will return 3. ~ represents bitwise NOT operator in JavaScript.

Basically ~3.14 is same as ~3, which is ~011 in binary => 100 or 4 in base 10. ~4 or ~100 is 011 or 3 in base 10.

edited Sep 26 '12 at 06:08

Bridge

answered Sep 26 '12 at 06:00

Ashwin Prabhu

Blender · Answer 2 · 2012-09-26T06:06:34.470

5

The tilde performs a bitwise NOT on the input after converting it to a 32-bit integer.

From the MDN:

Bitwise NOTing any number x yields -(x + 1). For example, ~5 yields -6.

In your case:

  ~~3.14
= -((~3.14) + 1)
= -(-(3.14 + 1) + 1)
= -(-(3 + 1) + 1)
= -(-4 + 1)
= -(-3)
= 3

edited Sep 26 '12 at 06:06

answered Sep 26 '12 at 06:01

Blender

score 5 · Answer 3 · edited May 23 '17 at 12:17

~ is the bitwise complement operator in JavaScript (and C/C++ and other languages). You can find more details here: How does the bitwise complement (~) operator work?

In this case:

Basically, ~n is equal to -n-1 for integers with Two's Complement representation.

3 Answers3