Error "Cannot Read Properties of Undefined (reading 'index')" in Grid

Updated on Mar 12, 2026

Environment

Product

Progress® Kendo UI for Angular Grid

Description

I encounter the error Cannot read properties of undefined (reading 'index') after updating my Angular app to v21. The error originates from ScrollerService2.onScroll in the Grid component.

Cause

Angular v21 enables zoneless mode by default, which affects some Kendo UI for Angular components. The Kendo UI for Angular components currently do not support zoneless mode. This mismatch triggers the error during certain operations like scrolling.

Solution

To resolve the issue, follow these steps to disable zoneless mode:

1. Install zone.js using npm:

   bash

   npm install zone.js

2. Add zone.js to the polyfills section of the angular.json file:

   json

   "styles": [
     "src/styles.css"
   ],
   "polyfills": [
     "@angular/localize/init",
     "zone.js"
   ]

3. Update the app.config.ts file to include the provideZoneChangeDetection function:

   typescript

   import {ApplicationConfig, importProvidersFrom, provideBrowserGlobalErrorListeners, provideZoneChangeDetection} from '@angular/core';
   import { provideRouter } from '@angular/router';
   import { provideAnimations } from '@angular/platform-browser/animations';
   import { routes } from './app.routes';
   
   export const appConfig: ApplicationConfig = {
     providers: [
       provideBrowserGlobalErrorListeners(),
       provideRouter(routes),
       provideZoneChangeDetection({ eventCoalescing: true }),
       provideAnimations()
     ],
   };

After you complete these steps, the Cannot read properties of undefined (reading 'index') error in the Kendo UI for Angular Grid is resolved.

See Also

• Kendo UI for Angular Grid Documentation
• Kendo UI for Angular FAQ on Zoneless Support
• Angular v21 Zoneless Change Detection