window.onload = function () {
  var symbol = document.getElementById("startID").innerText;
  fetch("/coin/"+symbol+"/").then(response => response.json()).then(
    function(jsonData) {
      points = generateDataPoints(jsonData)
      var chart = new CanvasJS.Chart("chartContainer",
      {
       data: [
       {
        type: "line",
        dataPoints: points
      }
      ]
    });
      chart.render();
    });
}

function generateDataPoints(coinArray) {
  var i, arr = [];
  for (i = 0; i < coinArray.length; i++) {
    arr.push({
      y: coinArray[i].prices,
      label: coinArray[i].date
    });
  }
  return arr;
}