Use browsers JSON.parse for parsing JSON.

sdk/lib/json/json.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart.json;
 
 // JSON parsing and serialization.
 
 /**
  * Error thrown by JSON serialization if an object cannot be serialized.
@@ skipping 17 matching lines @@
     if (cause != null) {
       return "Calling toJson method on object failed.";
     } else {
       return "Object toJson method returns non-serializable value.";
     }
   }
 }
 
 
 /**
- * Parses [json] and build the corresponding parsed JSON value.
+ * Parses [json] and builds the corresponding parsed JSON value.
  *
  * Parsed JSON values are of the types [num], [String], [bool], [Null],
  * [List]s of parsed JSON values or [Map]s from [String] to parsed
  * JSON values.
  *
- * The optional [revivier] function, if provided, is called once for each
- * object or list property parsed. The arguments are the property name
- * ([String]) or list index ([int]), and the value is the parsed value.
- * The return value of the revivier will be used as the value of that property
- * instead the parsed value.
+ * The optional [reviver] function, if provided, is called once for each object
+ * or list property parsed. The arguments are the property name ([String]) or
+ * list index ([int]), and the value is the parsed value.  The return value of
+ * the reviver will be used as the value of that property instead of the parsed
+ * value.  The top level value is passed to the reviver with the empty string as
+ * a key.
  *
  * Throws [FormatException] if the input is not valid JSON text.
  */
-parse(String json, [reviver(var key, var value)]) {
+external parse(String json, [reviver(var key, var value)]);
+
+_parse(String json, [reviver(var key, var value)]) {

[kasperl, 2013/02/06 07:07:11]

If this code is only used by the VM, it shouldn't live in the
platform-independent part of the library. That also goes for all the
implementation code below I guess.

[sra1, 2013/02/06 17:22:39]

The code can still be used by someone who needs their own custom JsonListener.
dart2js is smart enough to leave it out for 'normal' usage.

I intend to write a benchmark that uses JsonParser and the provided JsonListener
implementations to track dart2js compiled code performance which is currently
similar to VM performance.  Both are currently slower than the browser native
parser.

   BuildJsonListener listener;
   if (reviver == null) {
     listener = new BuildJsonListener();
   } else {
     listener = new ReviverJsonListener(reviver);
   }
   new JsonParser(json, listener).parse();
   return listener.result;
 }
 
@@ skipping 732 matching lines @@
         first = false;
       });
       sb.add('}');
       seen.removeLast();
       return true;
     } else {
       return false;
     }
   }
 }