Getting an arbitrary property from a JavaScript object in Dart

Ok, this was a fun one, happy holidays :)

It looks like Map is not a supported auto-conversion for package:js. So a couple of things:

1. Filed https://github.com/dart-lang/sdk/issues/28194
2. Sent your a PR introducing a workaround

For interested parties, we can use the browser-native Object.keys:

@JS()library example;import 'package:js/js.dart';/// A workaround to converting an object from JS to a Dart Map.Map jsToMap(jsObject) {  return new Map.fromIterable(    _getKeysOfObject(jsObject),    value: (key) => getProperty(jsObject, key),  );}// Both of these interfaces exist to call `Object.keys` from Dart.//// But you don't use them directly. Just see `jsToMap`.@JS('Object.keys')external List<String> _getKeysOfObject(jsObject);

And call it once we have an arbitrary JavaScript object:

var properties = jsToMap(toy.getData());print(properties);

I had to modify @matanlurey solution so it works on dart 2.12 and is recursive.

import 'dart:js';/// A workaround to deep-converting an object from JS to a Dart Object.Object jsToDart(jsObject) {  if (jsObject is JsArray || jsObject is Iterable) {    return jsObject.map(jsToDart).toList();  }  if (jsObject is JsObject) {    return Map.fromIterable(      getObjectKeys(jsObject),      value: (key) => jsToDart(jsObject[key]),    );  }  return jsObject;}List<String> getObjectKeys(JsObject object) => context['Object']    .callMethod('getOwnPropertyNames', [object])    .toList()    .cast<String>();