alt (method)

Abstract alt

• alt(def): Opt<T>

• Return this for Some, def for None. It represents an alternative on Opts.

  Parameters

  • def: Opt<T>

  Returns Opt<T>

  Example

  none.alt(some(0)) // Some(0)
  opt(1).alt(some(0)) // Some(1)
  none.alt(none) // None
  some(1).alt(none) // Some(1)
  

  Example

  It can be used to pick first from given possibly missing alternatives.

  type Handler = (_: number) => void;
  const userHandler: Opt<Handler> = opt(a => console.log('user handling', a));
  const systemHandler: Opt<Handler> = opt(a => console.log('system handling', a));
  const backupHandler: Opt<Handler> = opt(a => console.log('backup handling', a));
  const panicHandler: Handler = a => console.log('PANIC handling', a);
  const handler =
    userHandler
      .alt(systemHandler)
      .alt(backupHandler)
      .orElse(panicHandler);
  handler(250 + 64); // prints "user handling 314"