New helper: isPalindrome. Check if the number complies with the prope…

…rty of being written equally from left to right as from right to left.

src/helpers/index.ts

@@ -1,2 +1,3 @@
 export { divisors } from './divisors';
 export { isPrime } from './prime';
+export { isPalindrome } from './isPalindrome';

src/helpers/isPalindrome.test.ts

@@ -0,0 +1,12 @@
+import { isPalindrome } from './isPalindrome';
+
+describe('number is Palindrome', () => {
+  it('some numbers are palindrome', () => {
+    expect.assertions(4);
+
+    expect(isPalindrome(1)).toBe(true);
+    expect(isPalindrome(131)).toBe(true);
+    expect(isPalindrome(1221)).toBe(true);
+    expect(isPalindrome(123454321)).toBe(true);
+  });
+});

src/helpers/isPalindrome.ts

@@ -0,0 +1,4 @@
+export const isPalindrome = (n: number): boolean =>
+  n.toString().split('').reverse().join('') === n.toString();
+
+export default { isPalindrome };