What is the double tilde operator in JavaScript

Question

I m seeing this in some code  and I have no idea what it does   var jdn   function y  m  d      var tmp    m  lt   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

User · Answer

5 5         gt  -6   -6          gt  5   5 5         gt  5   same as Math floor 5 5      -5 5       gt  -5  NOT the same as Math floor -5 5   which would give -6     For more info  see    http   dreaminginjavascript wordpress com 2008 07 04 28

User · Answer

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

User · Answer

That    is a double NOT bitwise operator  It is used as a faster substitute for Math floor   for positive numbers  It does not return the same result as Math floor   for negative numbers  as it just chops off the part after the decimal  see other answers for examples of this

User · Answer

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  Update 2011-08  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

[javascript] What is the "double tilde" (~~) operator in JavaScript?

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