Getting An Arbitrary Property From A Javascript Object In Dart

Edit: Here is a minimal project that illustrates my issue. You can see the error described by serving it to the browser: pub get and then either pub serve (dartium) or pub build --

Solution 1:

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.MapjsToMap(jsObject) {
  returnnewMap.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);

Solution 2:

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.ObjectjsToDart(jsObject) {
  if (jsObject is JsArray || jsObject is Iterable) {
    return jsObject.map(jsToDart).toList();
  }
  if (jsObject is JsObject) {
    returnMap.fromIterable(
      getObjectKeys(jsObject),
      value: (key) =>jsToDart(jsObject[key]),
    );
  }
  return jsObject;
}

List<String> getObjectKeys(JsObjectobject) => context['Object']
    .callMethod('getOwnPropertyNames', [object])
    .toList()
    .cast<String>();