Implemented calculateMedian function

Author: alizada-dev

Sprint-1/fix/median.js

@@ -6,9 +6,28 @@
 // or 'list' has mixed values (the function is expected to sort only numbers).
 
 function calculateMedian(list) {
-  const middleIndex = Math.floor(list.length / 2);
-  const median = list.splice(middleIndex, 1)[0];
-  return median;
+
+  // first of all, checking if 'list' is an array
+  if (Array.isArray(list)) {
+    
+    const filteredArr = list.filter(x => typeof x === 'number');
+  
+    if (filteredArr.length < 2) {
+      return null;
+    }
+  
+    // using 'spread operator' copies the array without mutating it
+    const sortedList = [...filteredArr].sort((a, b) => a - b);
+  
+    const middleIndex = Math.floor(sortedList.length / 2);
+  
+    if (sortedList.length % 2 === 0) {
+      return (sortedList[middleIndex - 1] + sortedList[middleIndex]) / 2;
+    } else {
+      return sortedList[middleIndex]
+    }
+  }
+  return null;
 }
 
 module.exports = calculateMedian;