Question

I have a small dancer application which serves up some HTML (including the javascript to call the google charts API) and for other URLs queries a database and returns the data in encoded JSON in a form you can pass to google.visualization.DataTable. The javascript queries the dancer app for the JSON data then passes it into the google charts API – A simplified version is:

    <script type="text/javascript" src="https://www.google.com/jsapi"></script>
    <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
    <script type="text/javascript">

      google.load('visualization', '1.0', {'packages':['corechart']});
      google.setOnLoadCallback(initialize);

function initialize() {
    var res = $.ajax({
        url: "/data/2",
        dataType:"json",
        async: false,
        data: "{}",
        contentType: "application/json",
        error: function(jqXHR, textStatus, errorThrown) {
             alert('textStatus ' + textStatus);
             alert('errorThrown ' + errorThrown);
        }
    });
    jsonData = res.responseText;
    var data = new google.visualization.DataTable(jsonData);

    var chart = new google.visualization.BarChart(document.getElementById('chart_div'));
    chart.draw(data, {width: 400, height: 240});

}
    </script>

The problem is that some of the data returned by the Perl includes dates/timestamps and so should have the type set to “datetime”:

{"rows":[{"c":[{"v":"WHAT_CAN_I_PUT_HERE"},{"v":"2095"}]}],"cols":[{"type":"datetime","label":"DTU"},{"type":"number","label":"COUNT"}]}

In Javascript you could create a date to pass to the google charts API with:

new Date(2012, 1, 08, 09, 32, 0)

How can I send a date encoded in JSON from Perl such that the google charts API understands it? If you cannot what other options might be available to me?

Answer 1

JSON does not support datetime as a data types. But according to Google’s documentation, you can just send a string with this format:

JSON does not support JavaScript Date values (for example, “new Date(2008,1,28,0,31,26)”; the API implementation does. However, the API does now support a custom valid JSON representation of dates as a string in the following format: Date(year, month, day[,hour, minute, second[, millisecond]]) where everything after day is optional, and months are zero-based.

Google Chart Tools Datasource Protocol