In node.js: Export a function that builds the bowser object instead of trying to dereference navigator.userAgent, which probably doesn't exist.

src/bowser.js

@@ -1,7 +1,7 @@
 !function (name, definition) {
-  if (typeof define == 'function') define(definition)
+  if (typeof define == 'function') define(definition()(navigator.userAgent))
-  else if (typeof module != 'undefined' && module.exports) module.exports['browser'] = definition()
+  else if (typeof module != 'undefined' && module.exports) module.exports = definition()
-  else this[name] = definition()
+  else this[name] = definition()(navigator.userAgent)
 }('bowser', function () {
   /**
     * navigator.userAgent =>
@@ -14,13 +14,21 @@
     * iPad:    "Mozilla/5.0 (iPad; U; CPU OS 4_3_2 like Mac OS X; en-us) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8H7 Safari/6533.18.5",
     * Android: "Mozilla/5.0 (Linux; U; Android 2.3.4; en-us; T-Mobile G2 Build/GRJ22) AppleWebKit/533.1 (KHTML, like Gecko) Version/4.0 Mobile Safari/533.1"
     * Touchpad: "Mozilla/5.0 (hp-tabled;Linux;hpwOS/3.0.5; U; en-US)) AppleWebKit/534.6 (KHTML, like Gecko) wOSBrowser/234.83 Safari/534.6 TouchPad/1.0"
+    * PhantomJS: "Mozilla/5.0 (Macintosh; Intel Mac OS X) AppleWebKit/534.34 (KHTML, like Gecko) PhantomJS/1.5.0 Safari/534.34"
     */
 
-  var ua = navigator.userAgent
+  var t = true
-    , t = true
+
-    , ie = /msie/i.test(ua)
+  function detect(ua) {
+    function getFirstMatch(regexp) {
+      var match = ua.match(regexp);
+      return match && match[1];
+    }
+
+    var ie = /msie/i.test(ua)
       , chrome = /chrome/i.test(ua)
-    , safari = /safari/i.test(ua) && !chrome
+      , phantom = /phantom/i.test(ua)
+      , safari = /safari/i.test(ua) && !chrome && !phantom
       , iphone = /iphone/i.test(ua)
       , ipad = /ipad/i.test(ua)
       , touchpad = /touchpad/i.test(ua)
@@ -32,21 +40,24 @@
       , webkitVersion = /version\/(\d+(\.\d+)?)/i
       , o
 
-  function detect() {
-
     if (ie) return {
         msie: t
-      , version: ua.match(/msie (\d+(\.\d+)?);/i)[1]
+      , version: getFirstMatch(/msie (\d+(\.\d+)?);/i)
     }
     if (chrome) return {
         webkit: t
       , chrome: t
-      , version: ua.match(/chrome\/(\d+(\.\d+)?)/i)[1]
+      , version: getFirstMatch(/chrome\/(\d+(\.\d+)?)/i)
+    }
+    if (phantom) return {
+        webkit: t
+      , phantom: t
+      , version: getFirstMatch(/phantomjs\/(\d+(\.\d+)+)/i)
     }
     if (touchpad) return {
         webkit: t
       , touchpad: t
-      , version : ua.match(/touchpad\/(\d+(\.\d+)?)/i)[1]
+      , version: getFirstMatch(/touchpad\/(\d+(\.\d+)?)/i)
     }
     if (iphone || ipad) {
       o = {
@@ -58,7 +69,7 @@
       }
       // WTF: version is not part of user agent in web apps
       if (webkitVersion.test(ua)) {
-        o.version = ua.match(webkitVersion)[1]
+        o.version = getFirstMatch(webkitVersion)
       }
       return o
     }
@@ -66,33 +77,37 @@
         webkit: t
       , android: t
       , mobile: t
-      , version: ua.match(webkitVersion)[1]
+      , version: getFirstMatch(webkitVersion)
     }
     if (safari) return {
         webkit: t
       , safari: t
-      , version: ua.match(webkitVersion)[1]
+      , version: getFirstMatch(webkitVersion)
     }
     if (opera) return {
         opera: t
-      , version: ua.match(webkitVersion)[1]
+      , version: getFirstMatch(webkitVersion)
     }
     if (gecko) {
       o = {
           gecko: t
         , mozilla: t
-        , version: ua.match(/firefox\/(\d+(\.\d+)?)/i)[1]
+        , version: getFirstMatch(/firefox\/(\d+(\.\d+)?)/i)
       }
       if (firefox) o.firefox = t
       return o
     }
     if (seamonkey) return {
         seamonkey: t
-      , version: ua.match(/seamonkey\/(\d+(\.\d+)?)/i)[1]
+      , version: getFirstMatch(/seamonkey\/(\d+(\.\d+)?)/i)
     }
   }
 
-  var bowser = detect()
+  return function createBowser(ua) {
+    var bowser = detect(ua)
+    if (!bowser) {
+        return
+    }
 
     // Graded Browser Support
     // http://developer.yahoo.com/yui/articles/gbs
@@ -111,6 +126,6 @@
         (bowser.opera && bowser.version < 10.0)) {
       bowser.c = t
     } else bowser.x = t
-
+    return bowser;
-  return bowser
+  }
 })