JSFiddle - React, Tailwind, and code Playground

JavaScript

function Enum(baseEnum) {  
  return new Proxy(baseEnum, {
    get(target, name) {
      if (!baseEnum.hasOwnProperty(name)) {
        throw new Error(`"${name}" value does not exist in the enum`)
      }
      return baseEnum[name]
    },
    set(target, name, value) {
      throw new Error('Cannot add a new value to the enum')
    }
  })
}

const Sizes = Enum({
  Small: 'small',
  Medium: 'medium',
  Large: 'large',
})

const mySize = Sizes.Medium

console.log(mySize === Sizes.Medium) // logs true