Where would I use a bitwise operator in JavaScript?

Question

I've read 'what are bitwise operators?', so I know what bitwise operators are but I'm still not clear on how one might use them. Can anyone offer any real-world examples of where a bitwise operator would be useful in JavaScript?

Thanks.

Edit:

Just digging into the jQuery source I've found a couple of places where bitwise operators are used, for example: (only the & operator)

// Line 2756: event.which = (event.button & 1 ? 1 : ( event.button & 2 ? 3 : ( event.button & 4 ? 2 : 0 ) ));  // Line 2101 var ret = a.compareDocumentPosition(b) & 4 ? -1 : a === b ? 0 : 1; 

Answer 1

Example:

Parses hexadecimal value to get RGB color values.

var hex = 'ffaadd'; var rgb = parseInt(hex, 16); // rgb is 16755421   var red   = (rgb >> 16) & 0xFF; // returns 255 var green = (rgb >> 8) & 0xFF;  // 170 var blue  = rgb & 0xFF;     // 221   

Answer 2

I heavily use bitwise operators for numerical convertions in production scripts, because sometimes they're much faster than their Math or parseInt equivalents.

The price I have to pay is code readability. So I usualy use Math in development and bitwise in production.

You can find some performance tricks on jsperf.com.

As you can see, browsers don't optimize Math.ceil and parseInt for years, so I predict bitwise will be faster and shorter way to do things in furure as well.

Some further reading on SO...

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Bonus: cheat sheet for | 0 : an easy and fast way to convert anything to integer:

( 3|0 ) === 3;             // it does not change integers ( 3.3|0 ) === 3;           // it casts off the fractional part in fractionalal numbers ( 3.8|0 ) === 3;           // it does not round, but exactly casts off the fractional part ( -3.3|0 ) === -3;         // including negative fractional numbers ( -3.8|0 ) === -3;         // which have Math.floor(-3.3) == Math.floor(-3.8) == -4 ( "3"|0 ) === 3;           // strings with numbers are typecast to integers ( "3.8"|0 ) === 3;         // during this the fractional part is cast off too ( "-3.8"|0 ) === -3;       // including negative fractional numbers ( NaN|0 ) === 0;           // NaN is typecast to 0 ( Infinity|0 ) === 0;      // the typecast to 0 occurs with the Infinity ( -Infinity|0 ) === 0;     // and with -Infinity ( null|0 ) === 0;          // and with null, ( (void 0)|0 ) === 0;      // and with undefined ( []|0 ) === 0;            // and with an empty array ( [3]|0 ) === 3;           // but an array with one number is typecast to number ( [-3.8]|0 ) === -3;       // including the cast off of the fractional part ( [" -3.8 "]|0 ) === -3;   // including the typecast of strings to numbers ( [-3.8, 22]|0 ) === 0     // but an Array with several numbers is typecast to 0 ( {}|0 ) === 0;                // an empty object is typecast to 0 ( {'2':'3'}|0 ) === 0;         // or a not empty object ( (function(){})|0 ) === 0;    // an empty function is typecast to 0 too ( (function(){ return 3;})|0 ) === 0; 

and some magic for me:

3 | '0px' === 3;