context menu, editing connection

web/src/utility/common.js

@@ -0,0 +1,13 @@
+export class LoadingToken {
+  constructor() {
+    this.isCanceled = false;
+  }
+
+  cancel() {
+    this.isCanceled = true;
+  }
+}
+
+export function sleep(milliseconds) {
+  return new Promise(resolve => window.setTimeout(() => resolve(null), milliseconds));
+}