Source
void setupJsTypeCache() { // Cache the @JS Type. if (_atJsType == -1) { var uri = new Uri(scheme: "package", path: "js/js.dart"); var jsLibrary = mirrors.currentMirrorSystem().libraries[uri]; if (jsLibrary != null) { // @ JS used somewhere. var jsDeclaration = jsLibrary.declarations[new Symbol("JS")]; _atJsType = jsDeclaration.reflectedType; } else { // @ JS not used in any library. _atJsType = null; } } }