once in TS

once.ts

// tslint:disable-next-line:ban-types
export function once(fn: Function): Function {
  let executed = false;
  let result: any;

  // tslint:disable-next-line:only-arrow-functions
  return function() {
    if (executed) {
      return result;
    } else {
      executed = true;
      return result = fn.apply(null, arguments);
    }
  };
}