Add is-node?.

src/datomish/js_util.cljs

@@ -0,0 +1,14 @@
+;; This Source Code Form is subject to the terms of the Mozilla Public
+;; License, v. 2.0. If a copy of the MPL was not distributed with this
+;; file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+(ns datomish.js-util)
+
+(defn is-node? []
+  (try
+    (= "[object process]"
+       (.toString (aget js/global "process")))
+    (catch js/ReferenceError e
+      false)
+    (catch js/TypeError e
+      false)))