What does this: >> mean in JavaScript?
Seen in this context:
document.onkeydown = document.onkeyup = function(e,v,y,k) {
(i=e.keyCode-37)>>2 || (keys[i] = e.type[5]&&1||(0))
}
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bcm
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3I would fire whoever wrote that line of code. – Tony Dinh Jul 21 '16 at 16:15
4 Answers
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>> is the bitwise right shift operator.
For example: 4 >> 1 equals 2 because 4 is 100 in binary notation, which is shifted one bit to the right, giving us 10 = 2
Mårten Wikström
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what is the significance by getting the binary notation conversion, in this context, and then using the bitwise right shift operator? – bcm Apr 03 '11 at 07:23
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I don't see a reason for it. They could have written it as (i=e.keyCode-37)/4 instead, since right shifting two bits is essentially the same as dividing by four. – Mårten Wikström Apr 03 '11 at 07:33
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Left shift a << b Shifts a in binary representation b (< 32) bits to the left, shifting in zeros from the right.
Sign-propagating right shift a >> b Shifts a in binary representation b (< 32) bits to the right, discarding bits shifted off.
amosrivera
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(i=e.keyCode-37)>>2
This code is discarding the two least significant bits of i (similar to dividing by 4), and comparing the result to zero. This will be false when the key pressed is 37-40 (arrow keys), and true otherwise.
Phssthpok
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