lib: refactor variable declarations

PR-URL: #22643
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>

lib/internal/fs/utils.js

@@ -113,15 +113,15 @@ for (const name of Reflect.ownKeys(Dirent.prototype)) {
 }
 
 function copyObject(source) {
-  var target = {};
-  for (var key in source)
+  const target = {};
+  for (const key in source)
     target[key] = source[key];
   return target;
 }
 
 function getDirents(path, [names, types], callback) {
-  var i;
-  if (typeof callback == 'function') {
+  let i;
+  if (typeof callback === 'function') {
     const len = names.length;
     let toFinish = 0;
     callback = once(callback);