How to convert JavaScript object to Dart Map?

Question

I am looking for some reverse of new JsObject.jsify. Something, that would convert javascript Object back to Dart Map Is there somethi

Answer 1

Will convert recursively any JS object to a Dart map, list or scalar value:

/// js_interop.dart
import 'dart:js';

/// Converts the specified JavaScript [value] to a Dart instance.
dynamic convertToDart(value) {
  // Value types.
  if (value == null) return null;
  if (value is bool || value is num || value is DateTime || value is String) return value;

  // JsArray.
  if (value is Iterable) return value.map(convertToDart).toList();

  // JsObject.
  return new Map.fromIterable(getKeysOfObject(value), value: (key) => convertToDart(value[key]));
}

/// Gets the enumerable properties of the specified JavaScript [object].
List getKeysOfObject(JsObject object) => (context['Object'] as JsFunction).callMethod('keys', [object]);

Usage:

/// config.js
window.$environment = 'staging';
window.$config = {
  name: 'FooBar',
  params: {
    assets: ['css', 'js'],
    forceSsl: true
  }
};

/// main.dart
import 'dart:js' as js;
import 'js_interop.dart';

void main() {
  var environment = convertToDart(js.context[r'$environment']);
  assert(environment is String);
  assert(environment == 'staging');

  var config = convertToDart(js.context[r'$config']);
  assert(config is Map);
  assert(config.length == 2);

  assert(config['name'] is String);
  assert(config['name'] == 'FooBar');

  assert(config['params'] is Map);
  assert(config['params'].length == 2);

  assert(config['params']['forceSsl'] is bool);
  assert(config['params']['forceSsl'] == true);

  assert(config['params']['assets'] is List);
  assert(config['params']['assets'].length == 2);
  assert(config['params']['assets'].first == 'css');
  assert(config['params']['assets'].last == 'js');
}

Caveats: the created instance does not reflect the changes from the original JS object. If you need this feature, Alexandre Arduin's answer is the right one.