class ScrollComponent extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      scrollPosition: 0
    };
  }
  
  // ...
}

class ScrollComponent extends React.Component {
  // ...
  
  componentDidMount() {
    window.addEventListener('scroll', this.handleScroll);
  }
  
  handleScroll = () => {
    this.setState({
      scrollPosition: window.scrollY
    });
  }
  
  // ...
}

class ScrollComponent extends React.Component {
  // ...
  
  componentWillUnmount() {
    window.removeEventListener('scroll', this.handleScroll);
  }
  
  // ...
}