title: What is the error in sortBy function
body: <p>I am new to react and have problem sorting the datatable in react redered from json object. 
  I have rendered the datatable properly, but when i try to sort my datatable by using onClick on the cell component,the error says 
  "./src/App.js
    Line 34:  'tableData' is not defined  no-undef". </p>
  
  <p>Please point out what is the error I am making.The source code is :</p>
  
  <pre><code>  import React from 'react';
    import axios from 'axios';
    import {Table, Column, Cell} from 'fixed-data-table-2';
    import 'fixed-data-table-2/dist/fixed-data-table.css';
  
    class App extends React.Component {
      constructor (props) {
        super(props);
        this.state = { tableData : []};
        this.sortBy = this.sortBy.bind(this);
      }
  
      sortBy(sort_attr) {
        this.setState({
            tableData: tableData.sort('ascending')
            });
        }
  
  
    componentDidMount() {
        axios.get('https://drupal8.sample.com/my-api/get.json', {
              responseType: 'json'
          }).then(response =&gt; {
              this.setState({ tableData: response.data });
              console.log(this.state.tableData);
          });
        }
  
  
      render() {
        const rows = this.state.tableData;
        return (
          &lt;Table
          rowHeight={50}
          rowsCount={rows.length}
          width={500}
          height={500}
          headerHeight={50}&gt;
          &lt;Column
        header={&lt;Cell onClick= {this.sortBy}&gt;resourceID&lt;/Cell&gt;}
        columnKey="resourceID"
        cell={({ rowIndex, columnKey, ...props }) =&gt;
          &lt;Cell {...props}&gt;
            {rows[rowIndex][columnKey]}
          &lt;/Cell&gt;}
        width={200}
      /&gt;
        &lt;Column
        header={&lt;Cell&gt;resourceType&lt;/Cell&gt;}
        columnKey="resourceType"
        cell={({ rowIndex, columnKey, ...props }) =&gt;
          &lt;Cell {...props}&gt;
            {rows[rowIndex][columnKey]}
          &lt;/Cell&gt;}
        width={200}
      /&gt;
          &lt;Column
        header={&lt;Cell&gt;tenantName&lt;/Cell&gt;}
        columnKey="tenantName"
        cell={({ rowIndex, columnKey, ...props }) =&gt;
          &lt;Cell {...props}&gt;
            {rows[rowIndex][columnKey]}
          &lt;/Cell&gt;}
        width={200}
      /&gt;
        &lt;/Table&gt;
        );
      }
    }
  
    export default App;
  </code></pre>