Reading Custom CZML

CustomCzml.js

var viewer = new Cesium.Viewer('cesiumContainer');

viewer.clock.startTime = Cesium.JulianDate.fromIso8601('2015-10-30T12:00:00Z');
viewer.clock.stopTime = Cesium.JulianDate.fromIso8601('2015-10-30T23:00:00Z');
viewer.clock.currentTime = viewer.clock.startTime;
viewer.timeline.zoomTo(viewer.clock.startTime, viewer.clock.stopTime);

var czml = [
  {
    "id":"document",
    "version":"1.0"
  },
  {
    "id":"1",
    "name":"Name",
    "position":{
      "cartographicDegrees":[
        -75.5966,40.0386,0
      ]
    },
    "label":{
      "text":"Exton"
    },
    "stringProperty":"Some Value",
    "doubleProperty":{
      "epoch":"2015-10-30T12:00:00Z",
      "number":[
        0,1,
        39600,100
      ]
    }
  }
];
    
function processCustomProperties(entity, packet, dynamicObjectCollection, sourceUri) {
    var interval;
    var intervalString;

    var stringPropertyData = packet.stringProperty;
    if (Cesium.defined(stringPropertyData)) {
        intervalString = stringPropertyData.interval;
        if (Cesium.defined(intervalString)) {
            interval = Cesium.TimeInterval.fromIso8601({
                iso8601 : intervalString
            });
        }

        var stringProperty = entity.stringProperty;
        if (!Cesium.defined(stringProperty)) {
            entity.addProperty('stringProperty');
        }

        Cesium.CzmlDataSource.processPacketData(String, entity, 'stringProperty', stringPropertyData, interval, sourceUri);
    }
    var doublePropertyData = packet.doubleProperty;
    if (Cesium.defined(doublePropertyData)) {
        intervalString = doublePropertyData.interval;
        if (Cesium.defined(intervalString)) {
            interval = Cesium.TimeInterval.fromIso8601({
                iso8601 : intervalString
            });
        }

        var doubleProperty = entity.doubleProperty;
        if (!Cesium.defined(doubleProperty)) {
            entity.addProperty('doubleProperty');
        }

        Cesium.CzmlDataSource.processPacketData(Number, entity, 'doubleProperty', doublePropertyData, interval, sourceUri);
    }
}

Cesium.CzmlDataSource.updaters.push(processCustomProperties);

var czmlDataSource = new Cesium.CzmlDataSource();
czmlDataSource.load(czml);

viewer.dataSources.add(czmlDataSource);

var entity = czmlDataSource.entities.getById('1');

var lastDoublePropertyValue;
viewer.clock.onTick.addEventListener(function(clock) {
    var doublePropertyValue = entity.doubleProperty.getValue(clock.currentTime);
    if (lastDoublePropertyValue !== doublePropertyValue) {
        console.log(doublePropertyValue);
        lastDoublePropertyValue = doublePropertyValue;
    }
});