diff --git a/main.ts b/main.ts
index 848dc88..d2f7b4c 100644
--- a/main.ts
+++ b/main.ts
@@ -6,11 +6,11 @@ import { scan } from "rxjs/operators";
 // ****
 
 const source = interval(2000);
-const messageElement = document.querySelector('.message');
+const messageElement = document.querySelector(".message");
 
-const sourceMessage = x => `rxjs logo spun ${ x } times`;
-const log = x => messageElement.textContent = x;
+const sourceMessage = (x) => `rxjs logo spun ${x} times`;
+const log = (x) => (messageElement.textContent = x);
 
 source
-  .pipe(scan((_, count) => count + 1, 0))
-  .subscribe(message => log(sourceMessage(message)));
+  .pipe(scan((acc) => acc + 1, 0))
+  .subscribe((message) => log(sourceMessage(message)));
diff --git a/package-lock.json b/package-lock.json
index 54603a3..81f2b87 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,11 +1,11 @@
 {
   "name": "typescript-rxjs-webpack",
-  "version": "3.0.0",
+  "version": "4.0.0",
   "lockfileVersion": 2,
   "requires": true,
   "packages": {
     "": {
-      "version": "3.0.0",
+      "version": "4.0.0",
       "license": "MIT",
       "dependencies": {
         "rxjs": "^7.3.0"