What is change detection strategy in Angular?

Change detection in Angular is the process of updating the view or the component template with the new data when the model or the component’s data is updated. Angular has a powerful change detection mechanism that allows it to keep the view in sync with the component’s data.

There are two main strategies for change detection in Angular:

1. Default Change Detection Strategy: This is the default change detection strategy used by Angular. In this strategy, Angular uses a JavaScript engine’s ability to track changes in the component’s data. Angular performs change detection by running a digest cycle that checks if any changes have been made to the component’s data and updates the view accordingly.
2. OnPush Change Detection Strategy: This is an optimization strategy for change detection in Angular. In this strategy, Angular only performs change detection if an event or an observable fires or if the component’s inputs have changed. This strategy can lead to improved performance for applications with complex UI components and can help reduce the number of change detection cycles.

You can specify the change detection strategy for a component by using the changeDetection property of the component’s decorator.