// With callbacs:
class List extends Component {
  constructor(props) {
    super(props);
    props.items.map(item =>
      this.refsCallbacks[item.id] = (el) => this.refs.items[item.id] = el;
   );
   // also you can store refCallbacks in state.
  }
  componentWillReceiveProps(nextProps) {
    if (nextProps.items !== this.props.items) {
      nextProps.items.map(item => {
        if (this.refsCallbacks[item.id]) {
          return;
        }
        this.refsCallbacks[item.id] = (el) => this.refs.items[item.id] = el;
      });
    }
  }
  componentDidMount() {
    this.calculate();
  }
  componentDidUpdate() {
    this.calculate();
  }
  refsCallbacks = {};
  refs = {items: {}};
  calculate() {
    // Calculate width of elements and hide elements that overflow container
    this.refs.items.map(...); // Good
  }
  render() {
    const { items } = this.props;

    return (
        <div className='container'>
          {items.map(item =>
            <div
              ref={this.refCallbacks[item.id]}
              key={item.id}
              className='item'
            >
              {item.content}
            </div>
          )}
        </div>
    );
  }
}