feat: check leap year (service file)

src/pages/tools/time/check-leap-years/service.ts

@@ -0,0 +1,25 @@
+function isLeapYear(year: number): boolean {
+  return (year % 4 === 0 && year % 100 !== 0) || year % 400 === 0;
+}
+
+export function checkLeapYear(input: string): string {
+  if (!input) return '';
+
+  const years = input
+    .split('\n')
+    .map((year) => year.trim())
+    .filter((year) => year !== '');
+
+  const results = years.map((yearStr) => {
+    if (!/^\d{1,4}$/.test(yearStr)) {
+      return `${yearStr}: Invalid year`;
+    }
+
+    const year = Number(yearStr);
+    return `${year} ${
+      isLeapYear(year) ? 'is a leap year.' : 'is not a leap year.'
+    }`;
+  });
+
+  return results.join('\n');
+}