proxy_enum.js

const privateStatusEnum = {
  UNHARMED: 0,
  LIGHTLY_WOUNDED: 1,
  MODERATELY_WOUNDED: 2,
  SEVERELY_WOUNDED: 3,
  INCAPACITATED: 4,
};

const handler = {
  get: (obj, prop) => {
    if(!(prop in obj)) {
      throw new TypeError(`Invalid enum value: ${prop.toString()}`);
    }
    return obj[prop];
  },
  set: () => {
    throw new TypeError('Cannot set value of enum');
  },
};

const StatusEnum = new Proxy(privateStatusEnum, handler);

StatusEnum.UNHARMED; // 0
StatusEnum.UNHARMED = 123; // TypeError: Cannot set value of enum
StatusEnum.BADPROP; // TypeError: Invalid enum value: BADPROP
StatusEnum.BADPROP = 123; // TypeError: Cannot set value of enum