Add solution directories for exercises

12_findTheOldest/solution/findTheOldest-solution.js

@@ -0,0 +1,19 @@
+const findTheOldest = function (array) {
+    return array.reduce((oldest, currentPerson) => {
+        const oldestAge = getAge(oldest.yearOfBirth, oldest.yearOfDeath);
+        const currentAge = getAge(
+            currentPerson.yearOfBirth,
+            currentPerson.yearOfDeath
+        );
+        return oldestAge < currentAge ? currentPerson : oldest;
+    });
+};
+
+const getAge = function (birth, death) {
+    if (!death) {
+        death = new Date().getFullYear();
+    }
+    return death - birth;
+};
+
+module.exports = findTheOldest;