diff --git a/js/debug.js b/js/debug.js
new file mode 100644
index 0000000..4838911
--- /dev/null
+++ b/js/debug.js
@@ -0,0 +1,140 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+/**
+ * @fileoverview Utilities to debug JSPB based proto objects.
+ */
+
+goog.provide('jspb.debug');
+
+goog.require('goog.array');
+goog.require('goog.asserts');
+goog.require('goog.object');
+goog.require('jspb.Message');
+
+
+/**
+ * Turns a proto into a human readable object that can i.e. be written to the
+ * console: {@code console.log(jspb.debug.dump(myProto))}.
+ * This function makes a best effort and may not work in all cases. It will not
+ * work in obfuscated and or optimized code.
+ * Use this in environments where {@see jspb.Message.prototype.toObject} is
+ * not available for code size reasons.
+ * @param {jspb.Message} message A jspb.Message.
+ * @return {Object}
+ */
+jspb.debug.dump = function(message) {
+  if (!goog.DEBUG) {
+    return null;
+  }
+  goog.asserts.assert(message instanceof jspb.Message,
+      'jspb.Message instance expected');
+  /** @type {Object} */
+  var object = message;
+  goog.asserts.assert(object['getExtension'],
+      'Only unobfuscated and unoptimized compilation modes supported.');
+  return /** @type {Object} */ (jspb.debug.dump_(message));
+};
+
+
+/**
+ * Recursively introspects a message and the values its getters return to
+ * make a best effort in creating a human readable representation of the
+ * message.
+ * @param {*} thing A jspb.Message, Array or primitive type to dump.
+ * @return {*}
+ * @private
+ */
+jspb.debug.dump_ = function(thing) {
+  var type = goog.typeOf(thing);
+  if (type == 'number' || type == 'string' || type == 'boolean' ||
+      type == 'null' || type == 'undefined') {
+    return thing;
+  }
+  if (type == 'array') {
+    goog.asserts.assertArray(thing);
+    return goog.array.map(thing, jspb.debug.dump_);
+  }
+  var message = thing;  // Copy because we don't want type inference on thing.
+  goog.asserts.assert(message instanceof jspb.Message,
+      'Only messages expected: ' + thing);
+  var ctor = message.constructor;
+  var messageName = ctor.name || ctor.displayName;
+  var object = {
+    '$name': messageName
+  };
+  for (var name in ctor.prototype) {
+    var match = /^get([A-Z]\w*)/.exec(name);
+    if (match && name != 'getExtension' &&
+        name != 'getJsPbMessageId') {
+      var val = thing[name]();
+      if (val != null) {
+        object[jspb.debug.formatFieldName_(match[1])] = jspb.debug.dump_(val);
+      }
+    }
+  }
+  if (COMPILED && thing['extensionObject_']) {
+    object['$extensions'] = 'Recursive dumping of extensions not supported ' +
+        'in compiled code. Switch to uncompiled or dump extension object ' +
+        'directly';
+    return object;
+  }
+  var extensionsObject;
+  for (var id in ctor['extensions']) {
+    if (/^\d+$/.test(id)) {
+      var ext = ctor['extensions'][id];
+      var extVal = thing.getExtension(ext);
+      var fieldName = goog.object.getKeys(ext.fieldName)[0];
+      if (extVal != null) {
+        if (!extensionsObject) {
+          extensionsObject = object['$extensions'] = {};
+        }
+        extensionsObject[jspb.debug.formatFieldName_(fieldName)] =
+            jspb.debug.dump_(extVal);
+      }
+    }
+  }
+  return object;
+};
+
+
+/**
+ * Formats a field name for output as camelCase.
+ *
+ * @param {string} name Name of the field.
+ * @return {string}
+ * @private
+ */
+jspb.debug.formatFieldName_ = function(name) {
+  // Name may be in TitleCase.
+  return name.replace(/^[A-Z]/, function(c) {
+    return c.toLowerCase();
+  });
+};