SOURCE

const User = (function () {
    let _password

    class User {
        constructor(username, password) {
            _password = password
            this.username = username
        }

        login() {
            console.log(this.username, _password)
        }
    }
    return User
})()





const user = new User("123", "12345")
user.login()
console.log(user.username)