Cesium building loading (with height)

1. Load building

var promise=Cesium.GeoJsonDataSource.load('static/qunee/json/huangpuqu.json');
                promise.then(function(dataSource) {
                    self.$viewer.dataSources.add(dataSource);
                    var entities = dataSource.entities.values;
                    var colorHash = {};
                    for (var i = 0; i < entities.length; i++) {
                        var entity = entities[i];
                        var color =  Cesium.Color.RED.withAlpha(0.2);
                        entity.polygon.outlineColor=Cesium.Color.fromCssColorString('rgb(228,250,255)').withAlpha(0.7),
                        entity.polygon.material = color;
                        entity.polygon.outline = true;
                        entity.polygon.extrudedHeight =entity.properties.Floor._value*10;
                        entity.description="<div>"+entity.name+"</div>"
                    }
                })
                self.$viewer.flyTo(promise);

2.json data format

{"type":"FeatureCollection", "features": [
{"type":"Feature","geometry":{"type":"Polygon","coordinates":[[[121.4853406658038,31.247058287445054],[121.4852114601025,31.247076242618622],[121.48515766035248,31.246663496976442],[121.48528686519148,31.24665471027884],[121.4853406658038,31.247058287445054]]]},"properties":{"Name":" Dexin noodle restaurant ","Floor":"3"}},
{"type":"Feature","geometry":{"type":"Polygon","coordinates":[[[121.47433148624742,31.193284594140593],[121.47437454585763,31.193293888732274],[121.47441760314949,31.193330703415207],[121.47444989535822,31.193367487788922],[121.47446065576591,31.19342255819529],[121.4744498890723,31.19344087455375],[121.4744391215954,31.193468364251146],[121.47440682232205,31.193514139974507],[121.47436375953929,31.193541538718378],[121.47433146345989,31.19355062112739],[121.47428840231676,31.19355967325554],[121.47425610786017,31.19355040904155],[121.47422381342561,31.193541144844726],[121.47418075552352,31.19351350371729],[121.47416999203642,31.193495126768212],[121.47414846428381,31.193467546206442],[121.47413770158995,31.19343999591326],[121.47413770394746,31.1934124758826],[121.47413770630497,31.193384955844536],[121.47414847371384,31.19335746606902],[121.47415924033928,31.193339149639897],[121.47418077202583,31.19332086348544],[121.47423459971343,31.193293494832627],[121.47427766080735,31.1932844426407],[121.47430995606409,31.193284533534648],[121.47433148624742,31.193284594140593]]]},"properties":{"Name":"","Floor":"5"}}
]}