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, there. I just found that all of these numbers could be divided by 3, which rather slims down a string with the corresponding identifiers:

function(a){a=((this.Worker||0).prototype+'').length;return " i c s o f"[a/3]}

will do almost the same while golfing the script down to 82 bytes.

or if we divide by 5 and flooring the result:

function(a){a=((this.Worker||0).prototype+'').length;return 'i cs of'[a/5|0]}

still same result, yet only 78 bytes.

Update: will not run on older IEs, because they cant do String[number]...

Hi, nice idea! If we divide by 7 and use ||'i' for older ie and discard a we will get 76 bytes code:
function(){return '?icsof'[((this.Worker||0).prototype+'').length/7|0]||'i'}

you can save a byte removing the space between return and {f:a...

or return'?icsof'[...] in your alternate version

Thx!
I've just created another browser detection script using same magic on undefined ({}).toString.call(). Now it fully cross-browser(desktop and mobile). It free from Worker, but a bit longer.

https://gist.github.com/1123026

That's really cool. Since I'm working on mobile stuff, too, this will definitely be useful. Could we have support/detection for Symbian, Blackberry, Netfront Access, Obigo and some of the other mobile browsers?

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'.