How to convert JavaScript object to Dart Map?

Here's an adapter to handle a JsObject like a Map<String, dynamic> :

import 'dart:collection' show Maps;import 'dart:js';class JsMap implements Map<String,dynamic> {  final JsObject _jsObject;  JsMap.fromJsObject(this._jsObject);  operator [](String key) => _jsObject[key];  void operator []=(String key, value) {    _jsObject[key] = value;  }  remove(String key) {    final value = this[key];    _jsObject.deleteProperty(key);    return value;  }  Iterable<String> get keys => context['Object'].callMethod('keys', [_jsObject]);  // use Maps to implement functions  bool containsValue(value) => Maps.containsValue(this, value);  bool containsKey(String key) => keys.contains(key);  putIfAbsent(String key, ifAbsent()) => Maps.putIfAbsent(this, key, ifAbsent);  void addAll(Map<String, dynamic> other) {    if (other != null) {      other.forEach((k,v) => this[k] = v);    }  }  void clear() => Maps.clear(this);  void forEach(void f(String key, value)) => Maps.forEach(this, f);  Iterable get values => Maps.getValues(this);  int get length => Maps.length(this);  bool get isEmpty => Maps.isEmpty(this);  bool get isNotEmpty => Maps.isNotEmpty(this);}

You can generate json and parse it:

    Map map = JSON.decode(       context['JSON'].callMethod(           'stringify',           [context['map']]       )    );

If you want to do it deeply and handle also other cases then simple maps AND preserve functions (unlike the json solution) then use this simple function:

_toDartSimpleObject(thing) { if (thing is js.JsArray) {  List res = new List();  js.JsArray a = thing as js.JsArray;  a.forEach((otherthing) {    res.add(_toDartSimpleObject(otherthing));  });  return res; } else if (thing is js.JsObject) {  Map res = new Map();  js.JsObject o = thing as js.JsObject;  Iterable<String> k = js.context['Object'].callMethod('keys', [o]);   k.forEach((String k) {   res[k] = _toDartSimpleObject(o[k]);  });  return res; } else {  return thing; }}