Create 0523-continuous-subarray-sum.js

Added solution for continuous-subarray-sum in JS.

Author: aadil42

Diff for: javascript/0523-continuous-subarray-sum.js

@@ -0,0 +1,26 @@
+/**
+ * https://leetcode.com/problems/continuous-subarray-sum/
+ * Hasing
+ * Time O(n) | Space O(n)
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {boolean}
+ */
+var checkSubarraySum = function(arr, k) {
+    let sum = 0;
+    const remainderMap = new Map();
+    remainderMap.set(0,-1);
+  
+    for(let i = 0; i < arr.length;  i++) {
+        sum += arr[i];
+        if(remainderMap.has(sum%k)) {
+            if(i - remainderMap.get(sum%k) > 1) {
+                return true;
+            } 
+        } else {
+                remainderMap.set(sum%k,i);
+          }
+    }
+   
+    return false;
+  };