Enum Implementation using ES6 Proxies and Symbols

enum.js

function Enum(names) {
  let members = Object.create(null);
  
  members.tryParse = name => {
    if (!members[name]) {
      throw new Error(`Unable to parse '${name}' as an Enum member.`);
    }
    return members[name];
  };
  
  names.forEach(name => members[name] = Symbol(name));
  
  return new Proxy(members, {
    get: (target, name) => {
      if (!members[name]) {
        throw new Error(`Member '${name}' not found on the Enum.`);
      }
      return members[name];
    },
    set: (target, name, value) => {
      throw new Error('Adding new members to Enums is not allowed.');
    }
  });
}

@jzaefferer I like that! Mine was a bit of a quick hack for a specific use-case, but obviously doesn't factor in, e.g., serializability (looking back, I can't even remember why I went with Symbol values, vs. assigning a more traditional ordinal value). Thanks for sharing the improvements.