Update index.js

"parent" is now a property and no longer a method
Fixed the bounds so that the max chat messages do not exceed the MAX_LOG_COUNT value

limit-children/functions/index.js

@@ -23,13 +23,13 @@ const MAX_LOG_COUNT = 5;
 // Removes siblings of the node that element that triggered the function if there are more than MAX_LOG_COUNT.
 // In this example we'll keep the max number of chat message history to MAX_LOG_COUNT.
 exports.truncate = functions.database.ref('/chat/{messageid}').onWrite(event => {
-  const parentRef = event.data.ref.parent();
+  const parentRef = event.data.ref.parent;
   return parentRef.once('value').then(snapshot => {
-    if (snapshot.numChildren() > MAX_LOG_COUNT) {
+    if (snapshot.numChildren() >= MAX_LOG_COUNT) {
       let childCount = 0;
       const updates = {};
       snapshot.forEach(function(child) {
-        if (++childCount < snapshot.numChildren() - MAX_LOG_COUNT) {
+        if (++childCount <= snapshot.numChildren() - MAX_LOG_COUNT) {
           updates[child.key] = null;
         }
       });