diff --git a/chapter01/1.1 - Is Unique/isUnique.js b/chapter01/1.1 - Is Unique/isUnique.js
index 3321571..972387c 100644
--- a/chapter01/1.1 - Is Unique/isUnique.js	
+++ b/chapter01/1.1 - Is Unique/isUnique.js	
@@ -1,9 +1,9 @@
-var allUniqueChars = function(string) {
+const allUniqueChars = (string) => {
   
   // O(n^2) approach, no additional data structures used
   // for each character, check remaining characters for duplicates
-  for (var i = 0; i < string.length; i++) {
-    for (var j = i + 1; j < string.length; j++) {
+  for (let i = 0; i < string.length; i++) {
+    for (let j = i + 1; j < string.length; j++) {
       if (string[i] === string[j]) {
         return false; // if match, return false
       }