toJS property

JSPromise<JSAny?> get toJS

A JSPromise that either resolves once this Future completes or rejects with an object that contains its error.

The rejected object contains the original error as a JSBoxedDartObject in the property error and the original stack trace as a String in the property stack.

Implementation

JSPromise get toJS {
  return JSPromise(
    (JSFunction resolve, JSFunction reject) {
      this.then(
        (_) => resolve.callAsFunction(resolve),
        onError: (Object error, StackTrace stackTrace) {
          // TODO(srujzs): Can we do something better here? This is pretty much
          // useless to the user unless they call a Dart callback that consumes
          // this value and unboxes.
          final errorConstructor = globalContext['Error'] as JSFunction;
          final wrapper = errorConstructor.callAsConstructor<JSObject>(
            "Dart exception thrown from converted Future. Use the properties "
                    "'error' to fetch the boxed error and 'stack' to recover "
                    "the stack trace."
                .toJS,
          );
          wrapper['error'] = error.toJSBox;
          wrapper['stack'] = stackTrace.toString().toJS;
          reject.callAsFunction(reject, wrapper);
        },
      );
    }.toJS,
  );
}