Desktop browser detection script

annotated.js

/**
 * Modern desktop browser detector
 * 
 * @returns {Object}
 */
function (a) {
    // Worker.prototype.toString() magic see http://goo.gl/tD1jr
    a = ((this.Worker || 0).prototype + '').length;
    
    return {
        f: a == 36, // is Firefox?
        o: a == 33, // is Opera?
        s: a == 24, // is Safari?
        c: a == 15, // is Chrome?
        i: a == 9   // is IE?
    }
}

// Alternative version
function () {
    return '?icsof' [ 
           // same magic
           ((this.Worker||0).prototype+'').length / 7 | 0
           // fallback for ie6 :3
           ] || 'i'
}

index.js

function(a){a=((this.Worker||0).prototype+'').length;return{f:a==36,o:a==33,s:a==24,c:a==15,i:a==9}}
/* Alternative 75 byte version 
function(){return'?icsof'[((this.Worker||0).prototype+'').length/7|0]||'i'}
*/

LICENSE.txt

            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
                    Version 2, December 2004

 Copyright (C) 2011 azproduction

 Everyone is permitted to copy and distribute verbatim or modified
 copies of this license document, and changing it is allowed as long
 as the name is changed.

            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

  0. You just DO WHAT THE FUCK YOU WANT TO.

package.json

{
  "name": "browser",
  "description": "Desktop browser detection script",
  "keywords": [
    "browser",
    "detect",
    "detection",
    "firefox",
    "opera",
    "safari",
    "chrome",
    "ie"  
  ]
}

test.html

<pre id="br"></pre>
<script>
var b = function(a){a=((this.Worker||0).prototype+'').length;return{f:a==36,o:a==33,s:a==24,c:a==15,i:a==9}}();
document.getElementById('br').innerHTML = b.f && 'Firefox' || 
                                          b.o && 'Opera'   || 
                                          b.s && 'Safari'  || 
                                          b.c && 'Chrome'  || 
                                          b.i && 'Ie'      || 
                                                 '???'     ;
</script>

<!-- Alt version -->
<pre id="br2"></pre>
<script>
var b = function(){return'?icsof'[((this.Worker||0).prototype+'').length/7|0]||'i'}();
document.getElementById('br2').innerHTML = {f:'Firefox',o:'Opera',s:'Safari',c:'Chrome',i:'IE'}[b];
</script>

I own only iOS and Android, so i cant test on others. This is my test http://jsfiddle.net/azproduction/V4LeE/ i used to fill this table http://goo.gl/tD1jr you may use it.
This script is small and hacky but its not a good idea to identify a browser using a hack :)

usually I filter the essential portion out of the userAgent.

a good way, except for a fake User-Agent

I know - but it makes testing easier as an added value ;-)

@azproduction I know the gist description says "Desktop browser detection", but I thought I would mention that this fails on my iPhone 3gs (3.1.3) Safari 4 because it seems to lack Worker support. Also IE 10 reports [object WorkerPrototype] and so will be wrongly detected as Safari.

Hi!
In Firefox 26.0 (Ubuntu 13.04) return "isChrome'.