An ES6 module; alternative to iife syntax

block-module.js

{
  let planetsArr = [];
  let dwarfPlanets = [];
  let planetsLandedOn = 0;

  planetsArr.push("mercury", "Venus", "earth", "MArs", "jupiter", "saturn", "uranus", "Neptune");

  let planets = Object.create(null);

  planets.setPlanetsLandedOn = function(count) {
    if (count < 0 || count > planetsArr.length) {
      throw `I don't think so, bud. There are only ${planetsArr.length} planets`;
    } else {
      planetsLandedOn = count;
    }
  }

  planets.lowercasePlanets = function() {
    planetsArr = planetsArr.map( function(planet) {
      return planet.toLowerCase();
    });
  }

  planets.addDwarfPlanet = function(planetoid) {
    dwarfPlanets.push(planetoid);
  }

  planets.getPlanets = function() {
    return planetsArr;
  }

  window.SolarSystem = window.SolarSystem || {};
  SolarSystem.Planets = planets;

}