Update transcript-tracer.js

transcript-tracer.js

@@ -620,8 +620,8 @@ function handleSelection() {
   console.log(transcript.children[0].children);
 
   var nodes = [];
-  for (x in transcript.children) {
-    for (y in x.children) {
+  for (const x of transcript.children) {
+    for (const y of x.children) {
       nodes.push(y);
     }
   }