Update 0523-continuous-subarray-sum.js

Initializing Map as suggested.

Author: aadil42

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

@@ -8,9 +8,8 @@
  */
 var checkSubarraySum = function(arr, k) {
     let sum = 0;
-    const remainderMap = new Map();
-    remainderMap.set(0,-1);
-  
+    const remainderMap = new Map([ [0, -1] ]);
+    
     for(let i = 0; i < arr.length;  i++) {
         sum += arr[i];
         if(remainderMap.has(sum%k)) {