custom-component.ts

export class LongMessage extends React.Component {
  componentDidMount() {
    const newMessagesIndicator = document.getElementsByClassName('bpw-new-messages-indicator')[0]
    // If the "New Messages" div is present, we should not auto-scroll
    if (!newMessagesIndicator) {
      const messagesList = document.getElementsByClassName('bpw-msg-list')[0]
      messagesList.scrollTop = messagesList.scrollHeight
    }
  }
  render() {
    return (
      <div>
        {this.props.children} line 1<br />
        line 1<br />
        line 2<br />
        line 3<br />
        line 4<br />
        line 5<br />
        line 6<br />
        line 7<br />
      </div>
    )
  }
}