diff --git a/combination-sum/robinyoon-dev.js b/combination-sum/robinyoon-dev.js
new file mode 100644
index 0000000000..72c70ed2ed
--- /dev/null
+++ b/combination-sum/robinyoon-dev.js
@@ -0,0 +1,36 @@
+/**
+ * @param {number[]} candidates
+ * @param {number} target
+ * @return {number[][]}
+ */
+var combinationSum = function (candidates, target) {
+
+    const result = [];
+
+    function dfs(remainTarget, currentArray, currentIndex) {
+
+        if (remainTarget < 0) {
+            return;
+        }
+
+        if (remainTarget == 0) {
+            result.push([...currentArray]);
+            return;
+        }
+
+        // 백트래킹 탐색
+        for (let i = currentIndex; i < candidates.length; i++) {
+            currentArray.push(candidates[i]);
+
+            dfs(remainTarget - candidates[i], currentArray, i);
+
+            currentArray.pop();
+        }
+
+    }
+
+    dfs(target, [], 0);
+
+    return result;
+
+};
diff --git a/number-of-1-bits/robinyoon-dev.js b/number-of-1-bits/robinyoon-dev.js
new file mode 100644
index 0000000000..a47d965f44
--- /dev/null
+++ b/number-of-1-bits/robinyoon-dev.js
@@ -0,0 +1,19 @@
+/**
+ * @param {number} n
+ * @return {number}
+ */
+var hammingWeight = function (n) {
+    let count = 0;
+    let tempN = n;
+    while (tempN != 0) {
+        if (tempN & 1) {
+            // 비트 마스크(& 1): 앞의 비트들은 모두 0으로 무시하고, 맨 끝자리 비트만 추출하여 검사.
+            count++;
+        }
+        tempN = tempN >>> 1;
+        // >>: 부호 유지 우측 이동
+        // >>>: 부호 상관없이 0으로 채우는 우측 이동
+    }
+
+    return count;
+};
diff --git a/valid-palindrome/robinyoon-dev.js b/valid-palindrome/robinyoon-dev.js
new file mode 100644
index 0000000000..1f62f50254
--- /dev/null
+++ b/valid-palindrome/robinyoon-dev.js
@@ -0,0 +1,52 @@
+/**
+ * @param {string} s
+ * @return {boolean}
+ */
+var isPalindrome = function (s) {
+
+    //NOTE: 다음에는 투 포인터 방식으로 불어보겠습니다...
+
+    //0. 엣지케이스 대비: 빈칸인 경우.
+    if (s.trim() === '') {
+        return true;
+    }
+
+    //1. s를 array로 변환
+    const sArray = Array.from(s);
+
+    // 알파벳만 남기는 작업 
+    // (Alphanumeric characters include letters and numbers.)
+    const aAscii = 'a'.charCodeAt(0);
+    const zAscii = 'z'.charCodeAt(0);
+    const aUpperAscii = 'A'.charCodeAt(0);
+    const zUpperAscii = 'Z'.charCodeAt(0);
+    const zeroAscii = '0'.charCodeAt(0);
+    const nineAscii = '9'.charCodeAt(0);
+
+    const filteredArray = [];
+    for (let char of sArray) {
+        let charAscii = char.charCodeAt(0);
+
+        let isCharacter = (charAscii >= aAscii && charAscii <= zAscii) || (charAscii >= aUpperAscii && charAscii <= zUpperAscii) || (charAscii >= zeroAscii && charAscii <= nineAscii);
+
+        if (isCharacter) {
+            filteredArray.push(char);
+        }
+    }
+
+    // 대문자 -> 소문자로 변경하는 작업
+    const lowerArray = [];
+    for (let char of filteredArray) {
+        lowerArray.push(char.toLowerCase());
+    }
+
+    // reverse 해도 똑같은지 확인하는 작업
+    const reversedArray = [...lowerArray].reverse();
+
+    const originalString = lowerArray.join();
+    const reversedString = reversedArray.join();
+
+    return originalString === reversedString;
+
+};
+