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 (ad

Answer 1

I am doubtful that bitwise operation are particularly slow in javascript. Since such operations can map directly to CPU operations, which are themselves quite efficient, there doesn't appear to be any inherent characteristic of bitwise operations that would force them to be irremediably slow in javascript.
Edit December 2015: I stand corrected! The performance hit that Javascript suffers in regards to bitwise operations comes from the need of converting from float to int and back (as all numeric variables in Javascript are stored as floating point values). Thank you to Chad Schouggins for pointing that out.

Never the less, as indicated in several responses, there exist various applications of javascript which rely on bitwise operation (ex: crytography and graphics) and which are not particularly slow... (see silky and Snarfblam on this page). This suggests that while slower than C/C++ and other languages which translate directly bitwise ops to single native CPU instructions, bitwise operations are all that sluggish.

Let's never the less entertain the possibility that some particular reasons caused the various implementers of javascript hosts to implement bitwise ops in a fashion that makes these extremely slow, and see if this even matters...

Although javascript has been used for other purposes, the most common use of this language in in providing user interface type of services.
BTW, I do not mean this in any pejorative way at all; performing these smart UI functions, and considering various constraints imposed on the language and also the loose adherence to standards, has required -and keeps requiring- talented javascript hackers.
The point is that in the context of UI-type requirements, the need for any quantity of bitwise operations susceptible of exposing the slowness of javascript in handling such operations is uncommon at best. Consequently, for typical uses, programmers should use bitwise operations where and if this approach seems to flow well with overall program/data and they should do so with little concern for performance issues. In the unlikely case of performance bottleneck arising from bitwise use, one can always refactor things, but one is better off staying clear from early optimization.

The notable exception to the above is with the introduction of canvas, on modern browsers, we can expect that more primitive graphic functions will be required of javascript hosts, and such operations can require in some cases heavy doses of bitwise operations (as well as healthy does of math functions). It is likely that these services will eventually be supported by way of javascript libraries (and even end-up as languages additions). For such libraries the common smarts of the industry will have been put to use to figure out the most efficient approaches. Furthermore and if indeed there is a weakness in javascript performance with bitwise ops, we'll get some help, for I predict that the javascript implementations on various hosts (browsers) will be modified to improve this particular area. (This would follow the typical pattern of evolution of javascript, that we've seen over the years.)