maybe.js

function maybe(value) {
  const isEmpty = () => value === undefined || value === null;
  const nonEmpty = () => !isEmpty();
  return {
    map(f) { return isEmpty() ? this : maybe(f(value)) },
    getOrElse(n) { return isEmpty() ? n : value },
    isEmpty: isEmpty,
    nonEmpty: nonEmpty
  }
}

usage:

let p = { firstName: "foo" };
//let p = null;

// does throw a runtime error if p or firstName is null
//document.write(p.firstName.toUpperCase())

let chain = maybe(p)
  .map(p => p.firstName)
  .map(fn => fn.toUpperCase())
  .getOrElse("bar");

document.write(chain);