fix: Handle JS global in non-node environments (#125)

js/dune

@@ -10,4 +10,4 @@
   (names stubs))
  (js_of_ocaml
   (flags --no-sourcemap)
-  (javascript_files binaryen.es5.js postlude.js)))
+  (javascript_files prelude.js binaryen.es5.js postlude.js)))

js/postlude.js

@@ -1,2 +1,2 @@
-// Attach binaryen to our global
-global.binaryen = module.exports;
+// Attach binaryen to globalThis because JSOO wraps in an iife
+globalThis.binaryen = module.exports;

js/prelude.js

@@ -0,0 +1,11 @@
+if (typeof module === 'undefined') {
+  module = {};
+}
+
+if (typeof exports === 'undefined') {
+  exports = {};
+}
+
+if (typeof module.exports === 'undefined') {
+  module.exports = exports;
+}