Function parseStringYear

Parses a string into a CronYear.

Example

parseStringYear("1989"); // 1989,
parseStringYear("*"); // "*",
parseStringYear("1989/10"); // { every: 10, start: 1989 },
parseStringYear("?/10"); // { every: 10, start: "?" },
parseStringYear("1989,1991,2015,2020"); // [1989, 1991, 2015, 2020],
parseStringYear("1989-2020"); // { from: 1989, to: 2020 },
parseStringYear("1989,1991,2015,2020,1989-2020"); // [1989, 1991, 2015, 2020, { from: 1989, to: 2020 }],
parseStringYear("INVALID"); // undefined,
parseStringYear("1,2,3,4,INVALID"); // undefined,

Returns

A CronYear or undefined if invalid.