Builder pattern ES6 nodejs - node.js

Question

I've been having troubles when I try to call any builder "setter" methods
This is my code, User.js:
class User {
constructor(userBuilder) {
this.email = userBuilder.email;
this.name = userBuilder.name;
this.surname = userBuilder.surname;
this.photo = userBuilder.photo;
this.tokens = userBuilder.tokens;
this.authorized = userBuilder.authorized;
}
getEmail() {
return this.email;
}
getName() {
return this.name;
}
getSurname() {
return this.surname;
}
getPhoto() {
return this.photo;
}
getTokens() {
return this.tokens;
}
isAuthorized() {
return authorized;
}
static get UserBuilder() {
class UserBuilder {
constructor() {
this.email = null;
this.name = null;
this.surname = null;
this.photo = null;
this.tokens = null;
this.authorized = null;
}
email(email) {
this.email = email;
return this;
}
name(name) {
this.name = name;
return this;
}
surname(surname) {
this.surname = surname;
return this;
}
photo(photo) {
this.photo = photo;
return this;
}
tokens(tokens) {
this.tokens = tokens;
return this;
}
authorized(authorized) {
this.authorized = authorized;
return this;
}
build() {
return new User(this);
}
}
return UserBuilder;
}
}
module.exports = User
And my UserTest.spec.js:
process.env.NODE_ENV = 'test'
//Import User class
let User = require('../../../../main/com/auth/user/User');
// Import chai
let chai = require('chai');
// Tell chai that we'll be using the "should" style assertions.
chai.should();
describe('User', () => {
let user;
var email = "a#a";
var name = "a";
var surname = "a";
var photo = "p";
var authorized = true;
beforeEach(() => {
//Create new User object before each test
user = new User.UserBuilder()
.email(email)
.name(name)
.surname(surname)
.photo(photo)
.authorized(authorized)
.build();
});
it('returns the email', () => {
user.getEmail().should.equal(email)
});
it('returns the name', () => {
user.getName().should.equal(name)
});
it('returns the surname', () => {
user.getSurname().should.equal(surname)
});
it('returns the photo', () => {
user.getPhoto().should.equal(photo)
});
it('returns the authorized', () => {
user.getAuthorized().should.equal(authorized)
});
})
I get TypeError: user.email is not a function.
I've tried with UserBuilder outside User class:
In User.js
module.exports = {User: User, UserBuilder: UserBuilder}
In UserTest.spec.js
let {User} = require('../../../../main/com/auth/user/User');
let {UserBuilder} = require('../../../../main/com/auth/user/User');
user = new UserBuilder()
.email(email)
.name(name)
.surname(surname)
.photo(photo)
.authorized(authorized)
.build();
With the same result, what i'm doing wrong?? I can call build method, but I can't call any other methods.