This comment was originally written by aznaum...@gmail.com

I downloaded 1.0 SDK, and example (with different JSON URL input, using Tumblr API) and same behavior as I previously reported -- Dart SDK editor successfully runs but generated compiled javascript (did not try dart2js), just used the GUI generate javascript and then attempted to load page in Chrome browser.

Here is the code:

import 'dart:html';
import 'dart:js';

void main() {
  // Create a jsObject to handle the response.
  context['processData'] = (response) {
    print(response['tumblelog']['title']);
    querySelector('#pageboard').innerHtml = response['tumblelog']['title'];
  };

  ScriptElement script = new Element.tag("script");
  script.src = "http://azspot.net/api/read/json/?callback=processData";
  document.body.children.add(script);
}

//-----

In the SDK runs, but generated javascript produces this error:

Uncaught ReferenceError: DartObject is not defined
dart-sdk/lib/js/dart2js/js_dart2js.dart

// converts a Dart object to a reference to a native JS object
// which might be a DartObject JS->Dart proxy
Object _convertToDart(o) {
  if (JS('bool', '# == null', o) ||
      JS('bool', 'typeof # == "string"', o) ||
      JS('bool', 'typeof # == "number"', o) ||
      JS('bool', 'typeof # == "boolean"', o)) {
    return o;
  } else if (_isLocalObject(o)
      && (o is Blob || o is Event || o is KeyRange || o is ImageData
      || o is Node || o is TypedData || o is Window)) {
    // long line: dart2js doesn't allow string concatenation in the JS() form
    return JS('Blob|Event|KeyRange|ImageData|Node|TypedData|Window', '#', o);
  } else if (JS('bool', '# instanceof Date', o)) {
    var ms = JS('num', '#.getMilliseconds()', o);
    return new DateTime.fromMillisecondsSinceEpoch(ms);

//!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
//!!!!!!! Uncaught reference Error: DartObject is not defined
//!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

  } else if (JS('bool', '#.constructor === DartObject', o)) {
    return JS('', '#.o', o);
  } else {
    return _wrapToDart(o);
  }
}

Not clear if dart2js or dart:js issue.

Added Library-JS, Area-Dart2JS, Triaged labels.

I think I recognize this code from a recent CL from Justin.

Set owner to @justinfagnani.
Removed Area-Dart2JS label.
Added Area-Library label.

I'm getting "DartObject is undefined" as well. I'm using the "dart:js" library directly.

There's a another bug to remove DartObject and I wonder if this was done incompletely:
https://code.google.com/p/dart/issues/detail?id=14627

Looking at the JavaScript output, there are references to DartObject in two functions:
_convertToDart
_convertToJS_closure0

But there's no definition of DartObject that I can see.

It seems like there should be some end-to-end tests for JavaScript interop with dart2js?

This comment was originally written by @financecoding

Also hitting this error with.

Dart Editor version 1.0.3_r30939 (DEV)
Dart SDK version 1.0.3.0_r30939

This comment was originally written by youyou3...@gmail.com

Also getting this error using "google_maps" via pub.
Any news ?

This comment was originally written by Burak.Emir...@gmail.com

FWIW: I had some previously working code (pre-M4) that I am trying to get up to date again and then ran exactly into this error message. Then I checked the documentation and realized I have to include another script:

<script src="packages/browser/interop.js"></script>

That solved it for me.

This comment was originally written by douglas.damo...@gmail.com

Also receiving this error with 'dart:js' library.

Dart VM version: 1.0.0.10_r30798 (Mon Dec 2 10:26:47 2013) on "macos_x64"

This comment was originally written by youyou333...@gmail.com

<script src="packages/browser/interop.js"></script> has solved the "DartObject is undefined" for me.
thank you "skybr...@google.com"

This comment was originally written by @financecoding

fwiw, when I hit "DartObject is undefined" I noticed it might of been caused by the order the js scripts was included. Make sure interop.js is the first script. Example:

<script src="packages/browser/interop.js"></script>
<script type="application/dart">export 'package:polymer/init.dart';</script>
<script src="packages/browser/dart.js"></script>

This comment was originally written by douglas.da...@gmail.com

May I plus +1 Adam's tip here? It resolved my problem. To clarify, I iinterop'd from dart to an existing javascript library. I included <script src="packages/browser/interop.js"></script> after <script src="packages/browser/dart.js"></script> and the dart2js code didn't work until I reversed the order.

This comment was originally written by @financecoding

Agreed, this is one of those odd cases that is hard to remember or know what is the root cause of the issue. Maybe this should be posted on stack overflow and additional logging that could reference potential issue?

This comment was originally written by jirkad...@gmail.com

I posted it on SO as http://stackoverflow.com/questions/21492385/referenceerror-dartobject-is-not-defined

This comment was originally written by ernest.mi...@gmail.com

I noticed dat this solution (adding interop.js) is no longer working for 1.4.0-dev.6.2.
Refering to this script from HTML reports:

    packages/browser/interop.js is no longer needed for dart:js. See http://pub.dartlang.org/packages/browser.

What does solve it (again) is putting dart.js loading BEFORE loading my projects' dart file.