maybe.ts

declare interface MaybeFunction {
    <T1>(a: T1): T1;
    <T1, T2>(a: T1, b: (_: T1) => T2): T2;
    <T1, T2, T3>(a: T1, b: (_: T1) => T2, c: (_: T2) => T3): T3;
    <T1, T2, T3, T4>(a: T1, b: (_: T1) => T2, c: (_: T2) => T3, d: (_: T3) => T4): T4;
}

var maybe = <MaybeFunction>function() {
  let result = arguments[0];
  for (let i = 1, len = arguments.length; i < len; i++) {
    if (result == null) {
      return;
    }
    result = arguments[i](result);
  }
  return result;
}