问解析事件中json文件的数据结束后才会显示Amchart4

EN

chart.dataSource.url ="/static/json/{{ Post.Datasource|safe }}.json";
chart.dataSource.parser = new am4core.JSONParser();
chart.dataSource.reloadFrequency = 5000;
chart.dateFormatter.inputDateFormat = "i";
  var title = chart.titles.create();
//Funtion Date From and to
chart.dataSource.events.on("parseended", function(ev) {
      var data = ev.target.data;
    for (var i = 0; i < data.length; i++) {
      var startdate = new Date(data[0]["DATETIME"]).toISOString().replace("T"," ").replace("Z","").replace(".000","");
      var enddate = new Date(data[data.length -1]["DATETIME"]).toISOString().replace("T"," ").replace("Z","").replace(".000","");
  }
    title.html = (
        "Data from :" + '<span class="colors"> ' +
        startdate+ '</span> ' +
        " to " + '<span  class="colors">' +
        enddate + '</span>'
    );
});