Add existing to tracked

node_modules/@cesium/engine/Source/Scene/hasExtension.js

@@ -0,0 +1,19 @@
+import defined from "../Core/defined.js";
+
+/**
+ * Check if a specific extension is present on a JSON object. This can be used
+ * for either 3D Tiles extensions or glTF extensions
+ * @param {object} json The JSON object
+ * @param {string} extensionName The name of the extension, e.g. '3DTILES_implicit_tiling'
+ * @returns {boolean} True if the extension is present
+ * @private
+ */
+function hasExtension(json, extensionName) {
+  return (
+    defined(json) &&
+    defined(json.extensions) &&
+    defined(json.extensions[extensionName])
+  );
+}
+
+export default hasExtension;