improve code

README.md

@@ -28,4 +28,4 @@ implement the ability to filter and sort people in the table.
 - Implement a solution following the [React task guideline](https://github.com/mate-academy/react_task-guideline#react-tasks-guideline).
 - Use the [React TypeScript cheat sheet](https://mate-academy.github.io/fe-program/js/extra/react-typescript).
 - Open one more terminal and run tests with `npm test` to ensure your solution is correct.
-- Replace `<your_account>` with your Github username in the [DEMO LINK](https://<your_account>.github.io/react_people-table-advanced/) and add it to the PR description.
+- Replace `<your_account>` with your Github username in the [DEMO LINK](https://AlyonaV22.github.io/react_people-table-advanced/) and add it to the PR description.

src/constants/constants.ts

@@ -0,0 +1 @@
+export const CENTURIES = [16, 17, 18, 19, 20];

src/pages/PeoplePage.tsx

@@ -19,11 +19,14 @@ const isSelectedPeople = (
   if (query && query.trim()) {
     const newQuery = query.toLowerCase();
 
+    const isQuery = (field: string | null | undefined): boolean =>
+      field?.toLowerCase().includes(newQuery) ?? false;
+
     selectedPeople = selectedPeople.filter(
       person =>
-        person.name.toLowerCase().includes(newQuery) ||
-        person.motherName?.toLowerCase().includes(newQuery) ||
-        person.fatherName?.toLowerCase().includes(newQuery),
+        isQuery(person.name) ||
+        isQuery(person.motherName) ||
+        isQuery(person.fatherName),
     );
   }
 

src/types/sex.ts

@@ -0,0 +1,4 @@
+export enum Sex {
+  Male = 'm',
+  Female = 'f',
+}