Easy userAgent Access

gistfile1.js

var UA = (function(ua) {
        var browsers = {
          // Capture: Major#, #2, #3, #4, alphaBeta, alphaBeta#
            ie: /InternetExplorer/
          , fx: /firefox\/(\d+)(?:\.(\d+))?(?:\.(\d+))?(?:\.(\d+))?(?:(a|b)(\d*))?/i
          , cr: /Chrome/
          , sf: /Safari/
          , op: /Opera/
        }, key, ret, obj = {};

        for(key in browsers) {
          if(ret = ua.match(browsers[key])) {
            obj[key] = ret;
            return obj;
          }
        }

      }(navigator.userAgent));

とりあえず firefox だけ。