JavaScript StockChart with Line using JSON Data & AJAX

window.onload = function () {
  var dataPoints = [];
  var stockChart = new CanvasJS.StockChart("stockChartContainer", {
    exportEnabled: true,
    title: {
      text:"StockChart with Line using JSON Data"
    },
    subtitles: [{
      text:"Total Retail Sales of ACME "
    }],
    charts: [{
      axisX: {
        crosshair: {
          enabled: true,
          snapToDataPoint: true,
          valueFormatString: "MMM YYYY"
        }
      },
      axisY: {
        title: "Million of Dollars",
        prefix: "$",
        suffix: "M",
        crosshair: {
          enabled: true,
          snapToDataPoint: true,
          valueFormatString: "$#,###.00M",
        }
      },
      data: [{
        type: "line",
        xValueFormatString: "MMM YYYY",
        yValueFormatString: "$#,###.##M",
        dataPoints : dataPoints
      }]
    }],
    navigator: {
      slider: {
        minimum: new Date(2010, 00, 01),
        maximum: new Date(2018, 00, 01)
      }
    }
  });
  $.getJSON("https://canvasjs.com/data/gallery/stock-chart/grocery-sales.json", function(data) {
    for(var i = 0; i < data.length; i++){
      dataPoints.push({x: new Date(data[i].date), y: Number(data[i].sale)});
    }
    stockChart.render();
  });
}