Exploring Change Detection in Angular with Examples

Change detection is a core concept in Angular that is responsible for keeping the view in sync with the application state. In this blog, we will explore the basics of change detection and provide examples of how it works in Angular.

What is Change Detection in Angular?

Change detection is a process by which Angular detects changes in the application state and updates the view accordingly. It’s responsible for keeping the view up to date with the latest data in the application. Angular uses a tree-shaking algorithm to detect changes, which means that it checks the entire component tree for changes and updates the view accordingly.

How Change Detection Works in Angular?

Angular performs change detection automatically whenever a component’s input properties change or an asynchronous event is triggered. When a change is detected, Angular updates the view to reflect the new state of the application.

Consider the following example:

In this example, we have a simple CounterComponent that displays a counter and a button to increment it. Whenever the button is clicked, the count property is updated, and Angular automatically performs change detection to update the view.

OnPush Change Detection Strategy

The OnPush change detection strategy is an optimization technique that can be used to improve the performance of your application. When you use the OnPush strategy, Angular only performs change detection when a component’s input properties change or an event is triggered using the @Input decorator or the EventEmitter class.

Consider the following example:

In this example, we have set the changeDetection property to OnPush. This means that Angular only performs change detection when the count property is updated using the @Input decorator or the EventEmitter class.

When to Use OnPush Change Detection Strategy?

You should use the OnPush change detection strategy when you have a large component tree with a lot of components. By limiting the scope of change detection to only the components that need to be updated, you can significantly improve the performance of your application.

Here’s an example of how you might use the OnPush change detection strategy in a more complex component:

In this example, the UserComponent displays the user's name and address by using the AddressComponent. By using the OnPush change detection strategy, Angular only performs change detection when the user input property is updated, which in turn updates the view to display the new data.

change detection is a critical aspect of Angular that enables the framework to efficiently update the view whenever the application state changes. By using the OnPush change detection strategy, you can significantly improve the performance of your application, especially in scenarios where you have complex, nested component trees with a large number of components. It’s important to understand the basics of change detection and how it works in Angular to effectively optimize your application’s performance. By implementing the strategies and techniques discussed in this blog post, you can ensure that your Angular application is optimized for maximum efficiency and performance.

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