diff --git a/libraries/js/immutable/list.effekt b/libraries/js/immutable/list.effekt
index 5caa4ae607..a04285ef86 100644
--- a/libraries/js/immutable/list.effekt
+++ b/libraries/js/immutable/list.effekt
@@ -20,6 +20,14 @@ def foreach[A](l: List[A]) { f: A => Unit } : Unit = {
   }
 }
 
+def foreachIndex[T](list: List[T], i: Int){ f: (Int, T) => Unit}: Unit = {
+  list match {
+    case Nil() => ();
+    case Cons(head, tail) => f(i, head); foreachIndex(tail, i+1){f}
+
+  }
+}
+
 def map[A, B](l: List[A]) { f: A => B } : List[B] = {
   var acc = Nil[B]()
   l.foreach { el => acc = Cons(f(el), acc) }
diff --git a/libraries/js/mutable/array.effekt b/libraries/js/mutable/array.effekt
index a8f895c346..1750ba3cff 100644
--- a/libraries/js/mutable/array.effekt
+++ b/libraries/js/mutable/array.effekt
@@ -24,10 +24,13 @@ def initArray[T](size: Int) { index: Int => T}: Array[T] = {
 def initArray[T](list: List[T]): Array[T] = {
   val listSize = list.size();
   val arr = emptyArray(listSize);
-  var i = 0;
-  each(0,list.size())
+
+  foreachList(list, 0){(i, head) => put(arr, i, head)}
+  return arr;
 }
 
+
+
 extern pure def emptyArray[T](initialSize: Int): Array[T] =
   "(new Array(initialSize))"