loadGeojson

In a declarative manner, load GeoJSON concisely.

Usage

async function load() {
  const dataSource = await loadGeojson({
    url: 'geojson/land.json',
    dataSourceOptions: { clampToGround: true },
    onEntity(entity) {
      const properties = entity.properties.getValue(Cesium.JulianDate.now())
      console.log(properties)
    }
  })

  // The function loadGeojson is a pure function, so you need to manually use it.
  viewer.dataSources.add(dataSource)
}

async function loadPrimitive() {
  const primitive = await loadGeojson({
    url: 'geojson/water.json',
    // loadGeojson return what custom() returns when set the custom callback.
    custom(dataSource) {
      // ...
      dataSource.entities.values.forEach((e) => {
        // ...
      })
      return primitive
    }
  })

  viewer.scene.primitives.add(primitive)
}

For onEntity and custom, you can use them through methods rather than through arrow functions:

loadGeojson({
  url: 'geojson/water.json',

  custom: (dataSource) => { 
    console.log(this.url) // 'undefined'
  }, 

  custom(dataSource) { 
    console.log(this.url) // 'geojson/water.json'
  } 
})

This is useful when you need to access the local scope.

demo

Type Declarations

Details

export interface LoadGeojsonConfig<CustomReturns = any> {
  url: Parameters<Cesium.GeoJsonDataSource["load"]>[0]
  dataSourceOptions?: Parameters<Cesium.GeoJsonDataSource["load"]>[1]
  onEntity?: (entity: Cesium.Entity) => void
  custom?: (dataSource: Cesium.GeoJsonDataSource) => CustomReturns
}
/**
 * Load geojson without side effects.
 */
export declare function loadGeojson<T extends LoadGeojsonConfig>(
  config: T,
): Promise<
  T["custom"] extends (...args: any[]) => infer R ? R : Cesium.GeoJsonDataSource
>

Source

source • demo