Get the total number of days in a year

JavaScript version

const numberOfDays = (year) => ((year % 4 === 0 && year % 100 !== 0) || year % 400 === 0 ? 366 : 365);

// Or
const numberOfDays = (year) => (new Date(year, 1, 29).getDate() === 29 ? 366 : 365);

TypeScript version

const numberOfDays = (year: number): number => ((year % 4 === 0 && year % 100 !== 0) || year % 400 === 0 ? 366 : 365);

// Or
const numberOfDays = (year: number): number => (new Date(year, 1, 29).getDate() === 29 ? 366 : 365);