diff --git a/Sprint-1/JavaScript/calculateSumAndProduct/calculateSumAndProduct.js b/Sprint-1/JavaScript/calculateSumAndProduct/calculateSumAndProduct.js
index ce738c3..e971d3f 100644
--- a/Sprint-1/JavaScript/calculateSumAndProduct/calculateSumAndProduct.js
+++ b/Sprint-1/JavaScript/calculateSumAndProduct/calculateSumAndProduct.js
@@ -9,21 +9,20 @@
  *   "product": 30 // 2 * 3 * 5
  * }
  *
- * Time Complexity:
- * Space Complexity:
- * Optimal Time Complexity:
+ * Time Complexity:O(n)
+ * Space Complexity: O(1)
+ * Optimal Time Complexity:O(n)
  *
  * @param {Array<number>} numbers - Numbers to process
  * @returns {Object} Object containing running total and product
  */
+
+// The refactor code ....
 export function calculateSumAndProduct(numbers) {
   let sum = 0;
+  let product =1;
   for (const num of numbers) {
     sum += num;
-  }
-
-  let product = 1;
-  for (const num of numbers) {
     product *= num;
   }
 
@@ -32,3 +31,5 @@ export function calculateSumAndProduct(numbers) {
     product: product,
   };
 }
+
+// The refactor code is better because it combine two separate loop into one and calculate the sum & Product.
diff --git a/Sprint-1/JavaScript/findCommonItems/findCommonItems.js b/Sprint-1/JavaScript/findCommonItems/findCommonItems.js
index 5619ae5..df1f5ef 100644
--- a/Sprint-1/JavaScript/findCommonItems/findCommonItems.js
+++ b/Sprint-1/JavaScript/findCommonItems/findCommonItems.js
@@ -1,14 +1,26 @@
 /**
  * Finds common items between two arrays.
  *
- * Time Complexity:
- * Space Complexity:
- * Optimal Time Complexity:
+ * Time Complexity: O(n2)
+ * Space Complexity: O(n)
+ * Optimal Time Complexity:O(n)
  *
  * @param {Array} firstArray - First array to compare
  * @param {Array} secondArray - Second array to compare
  * @returns {Array} Array containing unique common items
  */
-export const findCommonItems = (firstArray, secondArray) => [
-  ...new Set(firstArray.filter((item) => secondArray.includes(item))),
-];
+
+//refactor code 
+export function findCommonItems (firstArray, secondArray){
+
+  const firstSet = new Set(firstArray);
+  const secondSet = new Set(secondArray);
+
+  const commonSet = firstSet.intersection(secondSet);
+  
+
+  return [...commonSet];
+}
+
+
+// This refactor code is better because it avoid to check every single item from two arrays for filter items & searching that each items includes in the second array . 
diff --git a/Sprint-1/JavaScript/hasPairWithSum/hasPairWithSum.js b/Sprint-1/JavaScript/hasPairWithSum/hasPairWithSum.js
index dd2901f..35ad203 100644
--- a/Sprint-1/JavaScript/hasPairWithSum/hasPairWithSum.js
+++ b/Sprint-1/JavaScript/hasPairWithSum/hasPairWithSum.js
@@ -1,14 +1,16 @@
 /**
  * Find if there is a pair of numbers that sum to a given target value.
  *
- * Time Complexity:
- * Space Complexity:
- * Optimal Time Complexity:
+ * Time Complexity:O(n2)
+ * Space Complexity:O(1)
+ * Optimal Time Complexity:O(n)
  *
  * @param {Array<number>} numbers - Array of numbers to search through
  * @param {number} target - Target sum to find
  * @returns {boolean} True if pair exists, false otherwise
  */
+
+/*
 export function hasPairWithSum(numbers, target) {
   for (let i = 0; i < numbers.length; i++) {
     for (let j = i + 1; j < numbers.length; j++) {
@@ -19,3 +21,27 @@ export function hasPairWithSum(numbers, target) {
   }
   return false;
 }
+  */
+
+//refactor code 
+
+export function hasPairWithSum(numbers,target){
+  const seen = new Set();
+
+  for (const num of numbers)
+  {
+    const needed = target-num;
+    if (seen.has(needed))
+    {
+      return true;
+    }
+    else
+    {
+      seen.add(num);
+    }
+  }
+
+}
+
+
+// The refactor code is better because it avoid nested loop but it create set so space complexity will be o(n).
\ No newline at end of file
diff --git a/Sprint-1/JavaScript/removeDuplicates/removeDuplicates.mjs b/Sprint-1/JavaScript/removeDuplicates/removeDuplicates.mjs
index dc5f771..2966f3d 100644
--- a/Sprint-1/JavaScript/removeDuplicates/removeDuplicates.mjs
+++ b/Sprint-1/JavaScript/removeDuplicates/removeDuplicates.mjs
@@ -1,13 +1,15 @@
 /**
  * Remove duplicate values from a sequence, preserving the order of the first occurrence of each value.
  *
- * Time Complexity:
- * Space Complexity:
- * Optimal Time Complexity:
+ * Time Complexity:O(n2)
+ * Space Complexity: O(n)
+ * Optimal Time Complexity: O(n) 
  *
  * @param {Array} inputSequence - Sequence to remove duplicates from
  * @returns {Array} New sequence with duplicates removed
  */
+
+/*
 export function removeDuplicates(inputSequence) {
   const uniqueItems = [];
 
@@ -34,3 +36,15 @@ export function removeDuplicates(inputSequence) {
 
   return uniqueItems;
 }
+  */
+
+//refactor code
+export function removeDuplicates(inputSequence) 
+{
+  const outputSequence = [...new Set(inputSequence)];
+  return outputSequence;
+}
+
+
+//The refactor code is better because it avoid the nested for loop operation ....
+