Modernize ES for-loops and remove problematic for-in loops

This slightly modifies the behaviour of errors (see init.js)

Change-Id: I1aab691d5b7e8167b6213378bdd9139c133202cd
diff --git a/dev/js/src/vc/fragment.js b/dev/js/src/vc/fragment.js
index f0c1397..ccc121e 100644
--- a/dev/js/src/vc/fragment.js
+++ b/dev/js/src/vc/fragment.js
@@ -142,9 +142,7 @@
         root.setAttribute('class','docGroup');
         root.setAttribute('data-operation', 'and');
 
-        for (let i in this._operands) {
-          root.appendChild(_doc(this._operands[i]));
-        };
+        this._operands.forEach(i => root.appendChild(_doc(i)));
       }
       else if (l == 1) {
         root = _doc(this._operands[0]);