Refs: Upgrade to React 16.3 version.

[AlmeroSteyn]

Really awesome example of using React to create an accessible HTML table!!

Thank you so much for taking the time to pusblish this. It is pure gold!

Spotted the use of a string ref. String refs should be treated as deprecated Legacy API: String Refs.

In this pull request I upgraded the example to use the new refs API from the freshly released React 16.3.

However, should this example be required for older versions of React the callback refs pattern should be used over string refs:

<div
    className="table-container"
    ref={container => { this.container = container }}
    tabIndex={this.state.tabindex}
    aria-labelledby={captionID}
>

Full code:

class Table extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      tabindex: null,
      rows: props.rows,
      sortedBy: null,
      sortDir: 'none'
    };
    this.sortBy = this.sortBy.bind(this);
  }

  sortBy(i) {
   //....
  }

  componentDidMount() {
    const {scrollWidth, clientWidth} = this.container;
    let scrollable = scrollWidth > clientWidth;
    this.setState({
      tabindex: scrollable ? '0' : null
    });
  }
  render() {
    const captionID = 'caption-' + Math.random().toString(36).substr(2, 9);
    return (
      <div>
        <div
          className="table-container"
          ref={container => { this.container = container }}
          tabIndex={this.state.tabindex}
          aria-labelledby={captionID}
        >
          <table>
            <caption id={captionID}>
              {this.props.caption}
              {this.state.tabindex === '0' &&
                <div>
                  <small>(scroll to see more)</small>
                </div>
              }
            </caption>
            <tbody>
              <tr>
                {this.props.headers.map((header, i) =>
                  <th
                    role="columnheader"
                    scope="col"
                    key={i}
                    aria-sort={this.state.sortedBy === i ? this.state.sortDir : 'none'}>
                    {header}
                    {this.props.sortable &&
                      <button
                        aria-label={`sort by ${header} in ${this.state.sortDir !== 'ascending' ? 'ascending' : 'descending'} order`}
                        onClick={() => this.sortBy(i)}>
                        <Arrow
                          sortDir={this.state.sortDir}
                          isCurrent={this.state.sortedBy === i}
                        />
                      </button>
                    }
                  </th>
                )}
              </tr>
              {this.state.rows.map((row, i) =>
                <tr key={i}>
                  {row.map((cell, i) =>
                    (this.props.rowHeaders && i < 1) ? (
                      <th scope="row" key={i}>{cell}</th>
                    ) : (
                      <td key={i}>{cell}</td>
                    )
                  )}
                </tr>
               )}
             </tbody>
          </table>
        </div>
        <div className="lists-container">
          <h2>{this.props.caption}</h2>
          {this.props.rows.map((row, i) =>
            <div key={i}>
              <h3>{row[0]}</h3>
              <dl>
                {this.props.headers.map((header, i) =>
                  i > 0 &&
                  <React.Fragment key={i}>
                    <dt>{header}</dt>
                    <dd>{row[i]}</dd>
                  </React.Fragment>
                )}
              </dl>
            </div>
          )}
        </div>
      </div>
    );
  }
}