diff --git a/contains-duplicate/moonjonghoo.js b/contains-duplicate/moonjonghoo.js
new file mode 100644
index 000000000..0da5c3a60
--- /dev/null
+++ b/contains-duplicate/moonjonghoo.js
@@ -0,0 +1,12 @@
+/**
+ * @param {number[]} nums
+ * @return {boolean}
+ */
+var containsDuplicate = function (nums) {
+  let nums_length = nums.length;
+  let hash = new Set(nums);
+  let hash_legnth = hash.size;
+  return nums_length === hash_legnth ? false : true;
+};
+
+containsDuplicate([1, 2, 3, 1]);
diff --git a/house-robber/moonjonghoo.js b/house-robber/moonjonghoo.js
new file mode 100644
index 000000000..dad457e69
--- /dev/null
+++ b/house-robber/moonjonghoo.js
@@ -0,0 +1,15 @@
+var rob = function (nums) {
+  const n = nums.length;
+  if (n === 0) return 0;
+  if (n === 1) return nums[0];
+
+  let dp = new Array(n).fill(0);
+  dp[0] = nums[0];
+  dp[1] = Math.max(nums[0], nums[1]);
+
+  for (let i = 2; i < n; i++) {
+    dp[i] = Math.max(dp[i - 1], dp[i - 2] + nums[i]);
+  }
+
+  return dp[n - 1];
+};
diff --git a/longest-consecutive-sequence/moonjonghoo.js b/longest-consecutive-sequence/moonjonghoo.js
new file mode 100644
index 000000000..76fc42fa7
--- /dev/null
+++ b/longest-consecutive-sequence/moonjonghoo.js
@@ -0,0 +1,21 @@
+var longestConsecutive = function (nums) {
+  const Set = new Set(nums);
+  let maxLength = 0;
+
+  for (let num of Set) {
+    if (!Set.has(num - 1)) {
+      let currentNum = num;
+      let count = 1;
+
+      // 연속된 숫자 탐색
+      while (Set.has(currentNum + 1)) {
+        currentNum++;
+        count++;
+      }
+
+      maxLen = Math.max(maxLength, count);
+    }
+  }
+
+  return maxLength;
+};
diff --git a/top-k-frequent-elements/moonjonghoo.js b/top-k-frequent-elements/moonjonghoo.js
new file mode 100644
index 000000000..a5be37cc5
--- /dev/null
+++ b/top-k-frequent-elements/moonjonghoo.js
@@ -0,0 +1,25 @@
+/**
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {number[]}
+ */
+var topKFrequent = function (nums, k) {
+  let map = new Map();
+
+  for (let num of nums) {
+    map.set(num, (map.get(num) || 0) + 1);
+  }
+
+  let freqArr = Array.from(map.entries());
+  freqArr.sort((a, b) => b[1] - a[1]);
+
+  let result = [];
+  for (let i = 0; i < k; i++) {
+    result.push(freqArr[i][0]);
+  }
+
+  return result;
+};
+
+topKFrequent([1, 1, 1, 2, 2, 3], 2);
+topKFrequent([1], 1);
diff --git a/two-sum/moonjonghoo.js b/two-sum/moonjonghoo.js
new file mode 100644
index 000000000..300ef6ce5
--- /dev/null
+++ b/two-sum/moonjonghoo.js
@@ -0,0 +1,18 @@
+/**
+ * @param {number[]} nums
+ * @param {number} target
+ * @return {number[]}
+ */
+var twoSum = function (nums, target) {
+  let map = new Map();
+  for (let i = 0; i < nums.length; i++) {
+    const complement = target - nums[i];
+    if (map.has(complement)) {
+      retuirn[(map.get(complement), i)];
+    }
+    map.set(nums[i], i);
+  }
+};
+
+console.log(twoSum([2, 7, 11, 15], 9));
+console.log(twoSum([3, 2, 4], 6));