~ in javascript

Question

Possible Duplicate:
How to: The ~ operator?

What's the ~ operator does in javascript?

input

alert(~1)

output is

-2 

input

~function () {}()

output is

-1

I never heard about ~ operator in javascript

Answer 1

https://developer.mozilla.org/en/JavaScript/Reference/Operators/Bitwise_Operators

Bitwise NOT ~ a Inverts the bits of its operand.

I guess its fairly odd that a function returns -1, but what would you expect anyway.

Answer 2

This is the bitwise not operator that inverts the value of every bit in the integer. In binary a signed integer has the following representation:

00000001 = 1
11111110 = -2

See this wikipedia article.

Answer 3

The bitwise NOT operator (~) will take its operand, convert it to a 32-bit integer, and will invert each bit so that each 0 becomes a 1 and vice versa.

http://james.padolsey.com/javascript/double-bitwise-not/