I'm seeing this in some code, and I have no idea what it does:
var jdn = function(y, m, d) {
var tmp = (m <= 2 ? -1 : 0);
return ~~((1461 * (y + 4800 + tmp)) / 4) +
~~((367 * (m - 2 - 12 * tmp)) / 12) -
~~((3 * ((y + 4900 + tmp) / 100)) / 4) +
d - 2483620;
};
What's the ~~
operator do?
This question is related to
javascript
The diffrence is very simple:
Long version
If you want to have better readability, use Math.floor
. But if you want to minimize it, use tilde ~~
.
There are a lot of sources on the internet saying Math.floor
is faster, but sometimes ~~
. I would not recommend you think about speed because it is not going to be noticed when running the code. Maybe in tests etc, but no human can see a diffrence here. What would be faster is to use ~~
for a faster load time.
Short version
~~
is shorter/takes less space. Math.floor
improves the readability. Sometimes tilde is faster, sometimes Math.floor
is faster, but it is not noticeable.
~(5.5) // => -6
~(-6) // => 5
~~5.5 // => 5 (same as Math.floor(5.5))
~~(-5.5) // => -5 (NOT the same as Math.floor(-5.5), which would give -6 )
For more info, see:
It hides the intention of the code.
It's two single tilde operators, so it does a bitwise complement (bitwise not) twice. The operations take out each other, so the only remaining effect is the conversion that is done before the first operator is applied, i.e. converting the value to an integer number.
Some use it as a faster alternative to Math.floor
, but the speed difference is not that dramatic, and in most cases it's just micro optimisation. Unless you have a piece of code that really needs to be optimised, you should use code that descibes what it does instead of code that uses a side effect of a non-operation.
With optimisation of the JavaScript engine in browsers, the performance for operators and functions change. With current browsers, using ~~
instead of Math.floor
is somewhat faster in some browsers, and not faster at all in some browsers. If you really need that extra bit of performance, you would need to write different optimised code for each browser.
See: tilde vs floor
Source: Stackoverflow.com