Implement requestMsg() for client-server-communication to receive data from the server

Change-Id: I6399679449199a3f5e75ca47348b4fd875f08142
diff --git a/dev/js/src/util.js b/dev/js/src/util.js
index 5df346b..5eab4b3 100644
--- a/dev/js/src/util.js
+++ b/dev/js/src/util.js
@@ -78,7 +78,7 @@
  * https://stackoverflow.com/questions/1349404/generate-random-string-characters-in-javascript#8084248
  */
 function randomID (len) {
-  var arr = new Uint8Array((len || 40) / 2)
+  let arr = new Uint8Array((len || 40) / 2)
   window.crypto.getRandomValues(arr)
   return Array.from(arr, _dec2hex).join('')
 };