JavaScript StockChart with MACD - Moving Average Convergence Divergence Indicator

window.onload = function () {
  var dps1 = [], dps2= [];
  var stockChart = new CanvasJS.StockChart("chartContainer",{
    theme: "light2",
    title:{
      text:"Technical Indicators: MACD"
    },
    subtitles: [{
      text: "Moving Average Convergence Divergence"
    }],
    charts: [{
      legend: {
        verticalAlign: "top",
        horizontalAlign: "left"
      },
      axisX: {
        tickLength: 0,
        lineThickness: 5,
        labelFormatter: function(e) {
          return "";
        }
      },
      axisY: {
        prefix: "$"
      },
      data: [{
        type: "candlestick",
        name: "Stock Price",
        yValueFormatString: "$#,###.##",
        dataPoints : dps1
      }],
    }],
    navigator: {
       data: [{
         dataPoints: dps2
       }],
      slider: {
        minimum: new Date(2018, 03, 01),
        maximum: new Date(2018, 05, 01)
      }
    }
  });
  $.getJSON("https://canvasjs.com/data/docs/ethusd2018.json", function(data) {
    for(var i = 0; i < data.length; i++){
      dps1.push({x: new Date(data[i].date), y: [Number(data[i].open), Number(data[i].high), Number(data[i].low), Number(data[i].close)]});
      dps2.push({x: new Date(data[i].date), y: Number(data[i].close)});
    }
    stockChart.render();
    var ema12 = calculateEMA(dps1, 12),
        ema26 = calculateEMA(dps1, 26),
        macd = [], ema9;
    for(var i = 0; i < ema12.length; i++) {
      macd.push({x: ema12[i].x, y: (ema12[i].y - ema26[i].y)});
    }
    var ema9 = calculateEMA(macd, 9);
    stockChart.addTo("charts", {height: 100, data: [{type: "line", name: "MACD", showInLegend: true, dataPoints: macd}], legend: {horizontalAlign: "left"}, toolTip: {shared: true}});
    stockChart.charts[1].addTo("data", {type: "line", name: "Signal", showInLegend: true, dataPoints: ema9});
  });
  function calculateEMA(dps,mRange) {
    var k = 2/(mRange + 1);
    emaDps = [{x: dps[0].x, y: dps[0].y.length ? dps[0].y[3] : dps[0].y}];
    for (var i = 1; i < dps.length; i++) {
      emaDps.push({x: dps[i].x, y: (dps[i].y.length ? dps[i].y[3] : dps[i].y) * k + emaDps[i - 1].y * (1 - k)});
    }
    return emaDps;
  }
}