getInitialprops3.js

class Page extends React.Component {
  static async getInitialProps(args) {
    return {
      ua: args.req ? args.req.headers['user-agent'] : navigator.userAgent,
    }
  }

  render() {
    const {ua} = this.props
    return (
        <UserAgentProvider ua={ua}>
          {/* Rest of Page */}
        </UserAgentProvider>
    )
  }
}