Sankey Diagram not getting value

by Lakshay Akula

HTML

<script type="text/javascript" src="https://www.google.com/jsapi"></script>
<div id="sankey_basic" style="width: 900px; height: 300px;"></div>

JavaScript

google.load('visualization', '1.1', {packages: ['sankey']});      
google.setOnLoadCallback(drawChart);

function drawChart() {
    var data = new google.visualization.DataTable();
    data.addColumn('string', 'From');
    data.addColumn('string', 'To');
    data.addColumn('number', 'Weight');
    data.addRows([
        [ 'A', 'X', 5 ],
        [ 'A', 'Y', 7 ],
        [ 'A', 'Z', 6 ],
        [ 'B', 'X', 2 ],
        [ 'B', 'Y', 9 ],
        [ 'B', 'Z', 4 ]
    ]);
             
    // Sets chart options.
    var options = {
        width: 600,
        sankey: {
            node: {
                interactivity: true
            }
        }
    };

    // Instantiates and draws our chart, passing in some options.
    var chart = new        
    google.visualization.Sankey(document.getElementById('sankey_basic'));
          
    google.visualization.events.addListener(chart, 'select', selectHandler);
      
    function selectHandler(e) {
    var selection = chart.getSelection();
    var message = '';
    
    for (var i = 0; i < selection.length; i++) {
        var item = selection[i];              
        if (item.row != null && item.column != null) {
            message += '{row:' + item.row + ',column:' + item.column + '}';
        } else if (item.row != null) {
            message += '{row:' + item.row + '}';
        } else if (item.column != null) {
            message += '{column:' + item.column + '}';
        }
    }
    
    if (message == '') {
        message = 'nothing';
    }

  alert('You selected ' + message);
}
    
    
    chart.draw(data, options);
}