Add existing to tracked

node_modules/@cesium/widgets/Source/subscribeAndEvaluate.js

@@ -0,0 +1,30 @@
+import knockout from "./ThirdParty/knockout.js";
+
+/**
+ * Subscribe to a Knockout observable ES5 property, and immediately fire
+ * the callback with the current value of the property.
+ *
+ * @private
+ *
+ * @function subscribeAndEvaluate
+ *
+ * @param {object} owner The object containing the observable property.
+ * @param {string} observablePropertyName The name of the observable property.
+ * @param {Function} callback The callback function.
+ * @param {object} [target] The value of this in the callback function.
+ * @param {string} [event='change'] The name of the event to receive notification for.
+ * @returns The subscription object from Knockout which can be used to dispose the subscription later.
+ */
+function subscribeAndEvaluate(
+  owner,
+  observablePropertyName,
+  callback,
+  target,
+  event,
+) {
+  callback.call(target, owner[observablePropertyName]);
+  return knockout
+    .getObservable(owner, observablePropertyName)
+    .subscribe(callback, target, event);
+}
+export default subscribeAndEvaluate;