make me login and registration code with database make as professional

const login = () => {
  fetch('/login', {
    method: 'post',
    body: {
      username: 'admin',
      password: 'admin'
    }
  })
}

const register = () => {
  fetch('/register', {
    method: 'post',
    body: {
      username: 'admin',
      password: 'admin',
      name: 'admin',
      email: 'admin@admin.com',
      phone: '123456789'
    }
  })
}