improved readability and comments added

Author: Elisabeth-Matulian

Sprint-1/fix/median.js

@@ -6,20 +6,25 @@
 // or 'list' has mixed values (the function is expected to sort only numbers).
 
 function calculateMedian(list) {
-  if (Array.isArray(list)) {
-    let newList = list.filter(item => typeof item === "number");
-    newList = newList.sort(function (a, b) {
-      return a - b;
-    });
-    if (newList.length > 0){
-      const middleIndex = Math.floor(newList.length / 2);
-      const median = newList[middleIndex]
-      if (newList.length % 2 !== 0) {
-        return median;
+  // if list is not an array, stop the function and return null
+  if (!Array.isArray(list)) {
+    return null;
+  }
+
+  // the list is filtered to get only the numbers, then sorted in ascending order
+  let newList = list.filter(item => Number.isFinite(item));
+  newList = newList.sort(function (a, b) { return a - b });
+  
+  // here we check if the list is empty, if not we calculate the median
+  if (newList.length > 0){
+    const middleIndex = Math.floor( newList.length / 2);
+    const median = newList[middleIndex]
+    if ( newList.length % 2 !== 0) {
+      return median;
     }
-      else return (newList[middleIndex - 1] + median) / 2}
-    else return null;}
-  else return null;
+  return (newList[middleIndex - 1] + median) / 2;
+  }
+  return null;
 }
 
 module.exports = calculateMedian;