cesiumjs-core-utilities

CesiumJS Core Utilities & Networking

Version baseline: CesiumJS v1.144+ (ES module imports, defaultValue removed in v1.134)

Breaking Change: defaultValue Removed (v1.134)

// WRONG (removed in v1.134)
const name = defaultValue(options.name, "default");
const opts = defaultValue(options, defaultValue.EMPTY_OBJECT);

// CORRECT (v1.134+)
import { Frozen } from "cesium";
const name = options.name ?? "default";
const opts = options ?? Frozen.EMPTY_OBJECT;

Frozen.EMPTY_OBJECT is Object.freeze({}) and Frozen.EMPTY_ARRAY is Object.freeze([]). Use them as safe defaults for options objects and array parameters.

Resource: HTTP Requests and Data Fetching

Resource is the unified class for all HTTP operations. It wraps URL construction, query parameters, headers, proxying, and retry logic.

Fetching Data

import { Resource } from "cesium";

// Static shorthand: accepts a URL string or options object
const jsonData = await Resource.fetchJson({ url: "https://api.example.com/data.json" });

// data: URIs work with Resource.fetchJson -- useful for inline GeoJSON or test fixtures
const dataUrl = "data:application/json," + encodeURIComponent(JSON.stringify(geojson));
const parsed = await Resource.fetchJson({ url: dataUrl });

// Instance-based: construct once, reuse for multiple fetches
const resource = new Resource({
  url: "https://api.example.com/features",
  queryParameters: { format: "json", limit: "100" },
  headers: { "Authorization": "Bearer my-token" },
});
const features = await resource.fetchJson();
const text = await resource.fetchText();           // string
const buffer = await resource.fetchArrayBuffer();  // ArrayBuffer
const blob = await resource.fetchBlob();           // Blob
const image = await resource.fetchImage();         // HTMLImageElement or ImageBitmap

Derived Resources and Template Values

import { Resource } from "cesium";

const api = new Resource({
  url: "https://tiles.example.com/{version}/tiles/{z}/{x}/{y}.png",
  templateValues: { version: "v2" },
  headers: { "X-Api-Key": "abc123" },
});

// getDerivedResource inherits headers, proxy, and retry settings
const tile = api.getDerivedResource({
  templateValues: { z: "10", x: "512", y: "384" },
});
const tileImage = await tile.fetchImage();

// Modify query parameters on an existing resource
resource.setQueryParameters({ access_token: "<access-token>" });
resource.appendQueryParameters({ extra: "param" });