How to extend CZML with custom properties.

I figures out to extend the Czml writer library to extend czml with a custom property like this:

}, …
//rest of path,position properties ect.


In javascript I can load the czml like this:

        var czmlDataSource = new Cesium.CzmlDataSource();
        czmlDataSource.load(czml, 'Built-in CZML');
        var vehicle = czmlDataSource.entities.getById("Vehicle");


I tried he following:



but do not seem to be able to find my custom data.

I also found var feeds = new Cesium.TimeIntervalCollectionProperty(); and can add the interval properties myself, but then I would need to parse the czml again, so I am wondering if there are extension points to make the czmldatasource accept my custom data field.

I belive i have found the answer by and the property updaters. Will take a look into those atleast.

I figured out the solution for me:

Cesium.CzmlDataSource.updaters.push((entity, packet, entityCollection, sourceUri) => {
var feedData = packet.feed;
if (!defined(feedData)) {

                var feed = entity.feed;
                if (!defined(feed)) {
                    entity.feed = feed = new Cesium.TimeIntervalCollectionProperty();

                if (isArray(feedData)) {
                    for (var i = 0, ii = feedData.length; i < ii; ++i) {
                        var data = feedData[i];
                            iso8601: data.interval,
                            isStartIncluded: true,
                            isStopIncluded: false,



my vechicle now has a feed property that change according to time.