Array.join() is really slow and has array memory allocation overhead... inste...

src/string.js

Index: src/string.js
===================================================================
--- src/string.js	(revision 3000)
+++ src/string.js	(working copy)
@@ -88,11 +88,11 @@
 // ECMA-262, section 15.5.4.6
 function StringConcat() {
   var len = %_ArgumentsLength();
-  var parts = new $Array(len + 1);
-  parts[0] = ToString(this);
-  for (var i = 0; i < len; i++)
-    parts[i + 1] = ToString(%_Arguments(i));
-  return parts.join('');
+  var this_string = ToString(this);

[Christian Plesner Hansen, 2009/10/02 05:47:12]

I would suggest using %StringAdd if len == 1 and using a StringBuilder (se
string.js) if there are more arguments.  That way the result becomes a flat
string rather than a chain of conses which we will have to flatten later.

+  for (var i = 0; i < len; i++) {
+    this_string = %StringAdd(this_string, ToString(%_Arguments(i)));
+  }
+  return this_string;
 }
 
 // Match ES3 and Safari