instanceOf: support Deno

Motivation #2566

src/jsutils/instanceOf.js

@@ -11,7 +11,7 @@ declare function instanceOf(
 
 // See: https://expressjs.com/en/advanced/best-practice-performance.html#set-node_env-to-production
 // See: https://webpack.js.org/guides/production/
-export default process.env.NODE_ENV === 'production'
+export default isProductionEnvironment()
   ? // istanbul ignore next (See: 'https://github.com/graphql/graphql-js/issues/2317')
     // eslint-disable-next-line no-shadow
     function instanceOf(value: mixed, constructor: mixed) {
@@ -44,3 +44,26 @@ spurious results.`,
       }
       return false;
     };
+
+/* global Deno */
+/* :: declare var Deno: any; */
+
+function isProductionEnvironment() {
+  try {
+    if (process.env.NODE_ENV === 'production') {
+      return true;
+    }
+  } catch (e) {
+    // ignore
+  }
+
+  try {
+    if (Deno.env.get('DENO_ENV') === 'production') {
+      return true;
+    }
+  } catch (e) {
+    // ignore
+  }
+
+  return false;
+}