Fixes #4222

tests/js/test2.nim

@@ -1,7 +1,8 @@
 discard """
   output: '''foo
 js 3.14
-7'''
+7
+1'''
 """
 
 # This file tests the JavaScript generator
@@ -29,3 +30,13 @@ proc test(x: C, T: typedesc): T =
   cast[T](x)
 
 echo 7.test(int8)
+
+# #4222
+const someConst = [ "1"]
+
+proc procThatRefersToConst() # Forward decl
+procThatRefersToConst() # Call bar before it is defined
+
+proc procThatRefersToConst() =
+  var i = 0 # Use a var index, otherwise nim will constfold foo[0]
+  echo someConst[i] # JS exception here: foo is still not initialized (undefined)