~ in javascript [duplicate]

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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开发者_如何学C

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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.

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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.

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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/