Improved JSON stringify.

test/mjsunit/json.js

 // Copyright 2009 the V8 project authors. All rights reserved.
 // 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
@@ skipping 260 matching lines @@
 var singleton = [];
 var multiOccurrence = [singleton, singleton, singleton];
 assertEquals("[[],[],[]]", JSON.stringify(multiOccurrence));
 
 assertEquals('{"x":5,"y":6}', JSON.stringify({x:5,y:6}));
 assertEquals('{"x":5}', JSON.stringify({x:5,y:6}, ['x']));
 assertEquals('{\n "a": "b",\n "c": "d"\n}',
              JSON.stringify({a:"b",c:"d"}, null, 1));
 assertEquals('{"y":6,"x":5}', JSON.stringify({x:5,y:6}, ['y', 'x']));
 
+// toJSON get string keys.
+var checker = {};
+var array = [checker];
+checker.toJSON = function(key) { return 1 + key; };
+assertEquals('["10"]', JSON.stringify(array));
+
 // The gap is capped at ten characters if specified as string.
 assertEquals('{\n          "a": "b",\n          "c": "d"\n}',
               JSON.stringify({a:"b",c:"d"}, null, 
                              "          /*characters after 10th*/"));
 
 //The gap is capped at ten characters if specified as number.
 assertEquals('{\n          "a": "b",\n          "c": "d"\n}',
               JSON.stringify({a:"b",c:"d"}, null, 15));
 
 // Replaced wrapped primitives are unwrapped.
@@ skipping 48 matching lines @@
     if (i < 16) {
       expected = "\\u000" + i.toString(16);
     } else {
       expected = "\\u00" + i.toString(16);
     }
   } else {
     expected = string;
   }  
   assertEquals('"' + expected + '"', encoded, "Codepoint " + i);
 }