A minor issue, though it was causing several tests to fail:

Java:
echo(69f) --> "69.0"

Javascript:
echo(69f) --> "69"

Ticket promoted to #2454 and assigned to andy

Another minor toStr difference is with Maps:

Java:
echo( ["Du":"de"] )  // --> [Du:de]

Javascript:
echo( ["Du":"de"] )  // --> [Du: de]

This works consistently between runtimes:

Obj:Obj? objs = ...
str := objs.isEmpty ? "[:]" : "[" + objs.join(",") |v, k| { "$k:$v" } + "]"

Here's a patch and a test for Float.toStr()

diff -r a77e9070251b src/sys/js/fan/Float.js
--- a/src/sys/js/fan/Float.js	Fri Sep 04 09:11:51 2015 -0400
+++ b/src/sys/js/fan/Float.js	Fri Sep 18 11:28:59 2015 +0100
@@ -157,7 +157,7 @@
   if (isNaN(self)) return "NaN";
   if (self == fan.sys.Float.m_posInf) return "INF";
   if (self == fan.sys.Float.m_negInf) return "-INF";
-  return ""+self;
+  return (fan.sys.Float.toInt(self) == self) ? self.toFixed(1) : ""+self;
 }
 
 fan.sys.Float.encode = function(self, out)
diff -r a77e9070251b src/testSys/fan/FloatTest.fan
--- a/src/testSys/fan/FloatTest.fan	Fri Sep 04 09:11:51 2015 -0400
+++ b/src/testSys/fan/FloatTest.fan	Fri Sep 18 11:28:59 2015 +0100
@@ -487,6 +487,9 @@
 
   Void testToStr()
   {
+    verifyEq(69.69f.toStr, "69.69")
+    verifyEq(69f.toStr,    "69.0")
+
     verifyEq(Float.posInf.toStr, "INF")
     verifyEq(Float.negInf.toStr, "-INF")
     verifyEq(Float.nan.toStr,    "NaN")

and a patch for Map.toStr()

diff -r a77e9070251b src/sys/js/fan/Map.js
--- a/src/sys/js/fan/Map.js	Fri Sep 04 09:11:51 2015 -0400
+++ b/src/sys/js/fan/Map.js	Fri Sep 18 11:30:07 2015 +0100
@@ -306,7 +306,7 @@
   this.$each(function(b)
   {
     if (s.length > 0) s += ", ";
-    s += b.key + ": " + b.val;
+    s += b.key + ":" + b.val;
   });
   return "[" + s + "]";
 }

Fix for the Map.toStr issue - try to keep issues on separate threads - easier to manage.

Ticket resolved in 1.0.68

Fixed

Thanks for all the patches Steve