left some comments to explain code and my error. Code is kind of confusing for outside readers, but you can kind of see what I'm trying to do.

dns.type.mx.js

@@ -45,20 +45,24 @@ exports.DNS_TYPE_MX = function (ab, packet, record) {
             
         } else {
 
+
+            // get data from uint8 array
             data = dv.getUint8(i, false);
+            // get the string from the data
             temp = String.fromCharCode(data);
             console.log("data at index " + i + ":" + temp);
             
+            // I need to place the '.' in the correct place. This is wrong though.
             if ((temp.trim() === ''  && i > 2) || (!temp.match(/^[a-zA-Z0-9._-]+$/) && i > 2)) {
                 s.exchange += ".";
             }
 
+            // filter out everything that isn't a valid character
             temp = temp.match(/^[a-zA-Z0-9._-]+$/);
 
             // if temp is null, do nothing
             if (temp === null){
 
-
                 // otherwise, append to s.exchange
             }else{
 
@@ -66,16 +70,12 @@ exports.DNS_TYPE_MX = function (ab, packet, record) {
 
             }
 
-            
+        }
-
-
     }
 
+    // the below code returns an empty string. 
     
-
+    // s.exchange = unpackLabels(new Uint8Array(ab), record.rdstart, { byteLength: 0, cpcount: 0, labels: [], name: '' }).labels;
-    }
-
-    // s.exchange = unpackLabels(new Uint8Array(ab), record.rdstart, { byteLength: 0, cpcount: 0, labels: [], name: '' }).name;
 
     return s;