I want to get all the coordinates of filled area of a polygon using Cesium js. I have tried polygon.hierarchy.valueOf() but not getting filled area coordinates.

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

var bluePolygon = viewer.entities.add({
    name : 'Blue polygon',
    polygon : {
        hierarchy : {
            positions : Cesium.Cartesian3.fromDegreesArray([-99.0, 30.0,
                                                            -85.0, 30.0,
                                                            -85.0, 40.0,
                                                            -99.0, 40.0]),
           
        },
        material : Cesium.Color.BLUE.withAlpha(0.5),
        height : 0,
        outline : true // height is required for outline to display
    }
});
console.log(JSON.stringify(bluePolygon.polygon.hierarchy.valueOf()));
viewer.zoomTo(viewer.entities);

Here is the sandcastle link