JSON.stringify improvement. Fast case in C++ for string arrays.

src/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 173 matching lines @@
     builder.push("[]");
     return;
   }
   if (!%PushIfAbsent(stack, value)) {
     throw MakeTypeError('circular_structure', $Array());
   }
   builder.push("[");
   var val = value[0];
   if (IS_STRING(val)) {
     // First entry is a string. Remaining entries are likely to be strings too.
-    builder.push(%QuoteJSONString(val));
-    for (var i = 1; i < len; i++) {
-      val = value[i];
-      if (IS_STRING(val)) {
-        builder.push(%QuoteJSONStringComma(val));
-      } else {
-        builder.push(",");
-        var before = builder.length;
-        BasicJSONSerialize(i, value[i], stack, builder);
-        if (before == builder.length) builder[before - 1] = ",null";
+    var array_string = %QuoteJSONStringArray(value);
+    if (!IS_UNDEFINED(array_string)) {
+      builder[builder.length - 1] = array_string;     
+    } else {
+      builder.push(%QuoteJSONString(val));
+      for (var i = 1; i < len; i++) {
+        val = value[i];
+        if (IS_STRING(val)) {
+          builder.push(%QuoteJSONStringComma(val));
+        } else {
+          builder.push(",");
+          var before = builder.length;
+          BasicJSONSerialize(i, value[i], stack, builder);
+          if (before == builder.length) builder[before - 1] = ",null";
+        }
       }
     }
   } else if (IS_NUMBER(val)) {
     // First entry is a number. Remaining entries are likely to be numbers too.
     builder.push(NUMBER_IS_FINITE(val) ? %_NumberToString(val) : "null");
     for (var i = 1; i < len; i++) {
       builder.push(",");
       val = value[i];
       if (IS_NUMBER(val)) {
         builder.push(NUMBER_IS_FINITE(val) 
@@ skipping 119 matching lines @@
 }
 
 function SetupJSON() {
   InstallFunctions($JSON, DONT_ENUM, $Array(
     "parse", JSONParse,
     "stringify", JSONStringify
   ));
 }
 
 SetupJSON();