Javascript enum using Object.freeze

enum.js

class Enum {
  constructor(...args) {
    if (args.length === 0) {
      throw new Error('Enum must be initialized with at least one argument');
    }
    let obj = (args.length === 1) ? args[0] : args;
    if (args.length > 1 || Array.isArray(obj)) {
      obj = Object.assign({}, ...obj.map((x) => ({ [x]: x })));
    }
    [...Object.entries(obj)].forEach((items) => {
      this[items[0]] = items[1];
    });
    Object.freeze(this);
  }
}

module.exports = Enum;

example.js

const Enum = require('./enum');

console.log('as args →', new Enum('a', 'b', 'c'));
console.log('as array →', new Enum(['a', 'b', 'c']));
console.log('as dict →', new Enum({ 'a': 'b', 'c': 'd' }));