Solution

src/scripts/main.js

@@ -1,3 +1,35 @@
 'use strict';
 
-// write your code here
+const populationArr = [...document.querySelectorAll('.population')];
+
+const parsedData = populationArr.map((e) => +e.textContent.replaceAll(',', ''));
+const totalPopulation = parsedData.reduce((acc, cur) => acc + cur, 0);
+
+const averagePopulation = Math.floor(totalPopulation / parsedData.length);
+
+document.querySelector('.total-population').textContent =
+  separateThousandsByComma(totalPopulation);
+
+document.querySelector('.average-population').textContent =
+  separateThousandsByComma(averagePopulation);
+
+function separateThousandsByComma(number) {
+  let tempNumber = number;
+  let result = '';
+  let counter = 0;
+
+  while (tempNumber > 0) {
+    const digit = tempNumber % 10;
+
+    tempNumber = Math.floor(tempNumber / 10);
+
+    result = digit + result;
+    counter++;
+
+    if (counter % 3 === 0 && tempNumber > 0) {
+      result = ',' + result;
+    }
+  }
+
+  return result;
+}