JavaScript Dynamic / Live StockChart with Stripline

window.onload = function () {
  var dataPoints = [], currentDate = new Date();
  var stockChart = new CanvasJS.StockChart("chartContainer",{
    theme: "light2",
    title:{
      text:"Dynamic StockChart with Stripline"
    },
    charts: [{
      axisX: {
         crosshair: {
          enabled: true,
          valueFormatString: "MMM DD, YYYY HH:mm:ss"
        }
      },
      axisY: {
        title: "Pageviews Per Second",
        stripLines: [{
          showOnTop: true,
          lineDashType: "dash",
          color: "#ff4949",
          labelFontColor: "#ff4949",
          labelFontSize: 14
        }]
      },
      toolTip: {
        shared: true
      },
      data: [{
        type: "line",
        name: "Pageviews",
        xValueFormatString: "MMM DD, YYYY HH:mm:ss",
        xValueType: "dateTime",
        dataPoints : dataPoints
      }]
    }],
    rangeSelector: {
      selectedRangeButtonIndex: 0,
      buttons: [{
        range: 1,
        rangeType: "minute",
        label: "1m"
      }, {
        range: 5,
        rangeType: "minute",
        label: "5m"
      }, {
        rangeType: "all",
        label: "All"
      }],
      inputFields: {
        enabled: false
      }
    }
  });
  var dataCount = 700, ystart = 50, interval = 1000, xstart = (currentDate.getTime() - (700 * 1000));
  updateChart(xstart, ystart, dataCount, interval);
  function updateChart(xstart, ystart, length, interval) {
    var xVal = xstart, yVal = ystart;
    for(var i = 0; i < length; i++) {
      yVal = yVal +  Math.round(5 + Math.random() *(-5-5));
      yVal = Math.min(Math.max(yVal, 5), 90);
      dataPoints.push({x: xVal,y: yVal});
      xVal += interval;
    }
    stockChart.options.charts[0].axisY.stripLines[0].value =  dataPoints[dataPoints.length - 1].y;
    stockChart.options.charts[0].axisY.stripLines[0].label = stockChart.options.charts[0].axisY.stripLines[0]["value"];
    xstart = xVal;
    dataCount = 1;
    ystart = yVal;
    stockChart.render();
    setTimeout(function() { updateChart(xstart, ystart, dataCount, interval); }, 1000);
  }
}