Type-Safe Enum in Javascript

FilterType.js

var FilterType = (function() {
    'use strict';
    
    var _type = function(type) {
        Object.defineProperties(this, {
            toString: { value: function() {
                return type;
            }},
            eq: { value: function(another) {
                return type === another.toString();
            }}
        });
    };

    return Object.create(Object.prototype, {
        AND: { value: new _type("AND"); },
        OR:  { value: new _type("OR"); }
    });
})();

Role.js

'use strict';

var Role = function(id) {
    Object.defineProperty(this, 'Id', { value: id });
};

Role.prototype = Object.create(Object.prototype, {
    toString: { value: function() {
        return this.Id;
    }},
    hasValue: { value: function(value) {
        if (typeof value === "string") {
            return this.Id === value;
        }
        return this === value;
    }}
});

Role.prototype.constructor = Role;

Object.defineProperties(Role, {
    GUEST:  { value: new Role('Guest')  },
    MEMBER: { value: new Role('Member') },
    ADMIN:  { value: new Role('Admin')  }
});