diff --git a/209-minimum-size-subarray-sum.js b/209-minimum-size-subarray-sum.js
new file mode 100644
index 000000000..0d4b41934
--- /dev/null
+++ b/209-minimum-size-subarray-sum.js
@@ -0,0 +1,25 @@
+// problem link https://leetcode.com/problems/minimum-size-subarray-sum/submissions/612844825/
+// time complexity is O(n).
+
+var minSubArrayLen = function(target, nums) {
+
+    let total = 0;
+    let min_length = Number.MAX_SAFE_INTEGER;
+    let left_pointer = 0;
+    for(let i = 0; i < nums.length; i++) {
+        
+        total += nums[i];
+        while(total >= target) {
+            min_length = Math.min(min_length, i + 1 - left_pointer);
+            total -= nums[left_pointer];
+            left_pointer = left_pointer+1;
+        }
+    }
+    
+   if(min_length == Number.MAX_SAFE_INTEGER) {
+       return 0;
+   } else {
+       return min_length;
+   }
+};
+
diff --git a/javascript/36-valid-sudoku.js b/javascript/36-valid-sudoku.js
new file mode 100644
index 000000000..57c0be474
--- /dev/null
+++ b/javascript/36-valid-sudoku.js
@@ -0,0 +1,30 @@
+
+// the time complexity is constant as we only going to have a 9*9 matrix.
+// problem link:  https://leetcode.com/problems/valid-sudoku
+
+var isValidSudoku = function(board) {
+    
+
+    let rows = [];
+    let columns = [];
+    let boxes = [];
+    for(let i = 0; i < board.length; i++) {
+        rows.push(new Set());
+        columns.push(new Set());
+        boxes.push(new Set());
+    }
+
+    for(let i = 0; i < board.length; i++) {
+        for(let j = 0; j < board[0].length; j++) {
+            const boxIndex = 3 * Math.floor(i/3) + Math.floor(j/3);
+            let curruntCell = board[i][j];
+            if(rows[i].has(curruntCell) || columns[j].has(curruntCell) || boxes[boxIndex].has(curruntCell)) return false;
+            if(curruntCell == '.') continue;
+            rows[i].add(curruntCell);
+            columns[j].add(curruntCell);
+            boxes[boxIndex].add(curruntCell);
+        }
+    }
+
+    return true;
+};
diff --git a/javascript/560-subarray-sum-equals-k.js b/javascript/560-subarray-sum-equals-k.js
new file mode 100644
index 000000000..ff9d4e71d
--- /dev/null
+++ b/javascript/560-subarray-sum-equals-k.js
@@ -0,0 +1,23 @@
+// Problem link https://leetcode.com/problems/subarray-sum-equals-k
+// Time Complexity: O(n)
+
+
+var subarraySum = function(nums, k) {
+    
+   
+ 
+const prefixMap = {};
+let totalSubArray = 0;
+let ongoingSum = 0;
+
+prefixMap[0] = 1;
+for(let i = 0; i < nums.length; i++) {
+    ongoingSum += nums[i];
+    if(prefixMap[ongoingSum - k]){
+        totalSubArray += prefixMap[ongoingSum - k];
+    }
+    prefixMap[ongoingSum] = (prefixMap[ongoingSum] ? prefixMap[ongoingSum] + 1: 1);
+}
+
+return totalSubArray;
+};