Add some basic exception reporting for emscripten

build-data/web/index.html

@@ -287,7 +287,10 @@
         },
       };
       Module.setStatus("Downloading...");
-      window.onerror = function (event) {
+      window.onerror = function (event, source, lineno, colno, error) {
+        if (typeof error === 'number' && Module.getExceptionMessage) {
+          console.log(Module.getExceptionMessage(error));
+        }
         alert("Exception thrown, see JavaScript console.");
       };
       window.onbeforeunload = (e) => {

src/emscripten_exception.cpp

@@ -0,0 +1,13 @@
+#if defined(EMSCRIPTEN)
+#include <emscripten/bind.h>
+
+std::string getExceptionMessage( intptr_t exceptionPtr )
+{
+    return std::string( reinterpret_cast<std::exception *>( exceptionPtr )->what() );
+}
+
+EMSCRIPTEN_BINDINGS( Bindings )
+{
+    emscripten::function( "getExceptionMessage", &getExceptionMessage );
+}
+#endif