windowExists function fix

gulpfile.js

@@ -34,7 +34,13 @@ function js() {
     .pipe(replace("MAILGO_VERSION", version))
     .pipe(replace("MAILGO_STYLE", cssMinContent))
     .pipe(babel())
-    .pipe(uglify())
+    .pipe(
+      uglify({
+        mangle: {
+          keep_fnames: true // keep function names
+        }
+      })
+    )
     .pipe(
       rename({
         suffix: ".min"

src/mailgo.js

@@ -1,6 +1,8 @@
-// @flow
 const V = "MAILGO_VERSION";
 
+// window exists
+const windowExists = () => window && typeof window !== "undefined";
+
 // links
 const MAILTO = "mailto:";
 const TEL = "tel:";
@@ -813,9 +815,6 @@ const encodeEmail = email => btoa(email);
 // getE shorthand
 const getE = id => document.getElementById(id);
 
-// window exists
-const windowExists = () => window && typeof window !== "undefined";
-
 // get display value
 const getDisplay = id => getE(id).style.display;