ua.js

var ua = (function(){
    var ua = {};
    var navigator = window.navigator;
    var platforms = [
        { property: 'platform', regex: /iPhone/i, identity: 'iPhone' },
        { property: 'platform', regex: /iPod/i, identity: 'iPod' },
        { property: 'userAgent', regex: /iPad/i, identity: 'iPad' },
        { property: 'userAgent', regex: /Blackberry/i, identity: 'Blackberry' },
        { property: 'userAgent', regex: /Android/i, identity: 'Android' },
        { property: 'platform', regex: /Mac/i, identity: 'Mac' },
        { property: 'platform', regex: /Win/i, identity: 'Windows' },
        { property: 'platform', regex: /Linux/i, identity: 'Linux' }
    ];
    for(var i=0, l=platforms.length, platform; i<l; i++){
        platform = platforms[i];
        ua[platform.identity] = platform.regex.test(navigator[platform.property]);
    }
    ua.AndroidTablet = ua.Android && !/mobile/i.test(navigator.userAgent);
    ua.tablet = ua.iPad || ua.AndroidTablet;
    return ua;
})();

/* test */

function test(){
    function log(text){
        console.log(text)
    }
    log('iPhone: ' + ua.iPhone);
    log('iPad: ' + ua.iPad);
    log('iPod: ' + ua.iPod);
    log('Blackberry: ' + ua.Blackberry);
    log('Android: ' + ua.Android);
    log('Mac: ' + ua.Mac);
    log('Windows: ' + ua.Windows);
    log('Linux: ' + ua.Linux);
    log('AndroidTablet: ' + ua.AndroidTablet);
    log('tablet: ' + ua.tablet);
}

test();