Performance of bitwise operators in javascript

Question

One of the main ideas behind using bitwise operators in languages like C++/java/C# is that they're extremely fast. But I've heard that in javascript they're very slow (admittedly a few milliseconds probably doesn't matter much today). Why is this so?

(this question discusses when bitwise operators are used, so I'm changing the focus of this question to performance.)

Answer 1

This is quite an old question, but no one seemed to answer the updated version.

The performance hit that you get with JavaScript that doesn't exist in C/C++ is the cast from floating point representation (how JavaScript strores all of its numbers) to a 32 bit integer to perform the bit manipulation and back.

Answer 2

Nobody uses hex anymore?

function hextoRgb(c) {
    c = '0x' + c.substring(1);
    return [(c >> 16) & 255, (c >> 8) & 255, c & 255]; 
}

var c1 = hextoRgb('#191970');
alert('rgb(' + c1.join(',') + ')');

Answer 3

I use bitwise shift of zero in JS to perform quick integer truncation:

var i=3.141532;
var iTrunc=i>>0; //3