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>

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