Enum-like structure in es2015

index.js

const Shape = {
  Triangle: new Symbol()
};

// Demo func
function getArea(shape, options) {
  var area = 0;
  
  switch (shape) {
    case Shape.Triangle:
      area = .5 * options.w * options.h;
      break;
  }
  
  return area;
}

getArea(Shape.Triangle, {w: 100, h: 50});