Angular Interview Practice

How does Angular detect changes in components?

1. By using two-way data binding exclusively

2. Through unidirectional data flow by traversing the component tree

3. By checking only user input

4. By reloading the entire application on changes

The correct answer is: Through unidirectional data flow by traversing the component tree

Angular detects changes in components primarily through a process known as change detection, which is effectively implemented by traversing the component tree using unidirectional data flow. In this model, data flows in one direction, from parent components to child components. Angular maintains a tree structure of components and monitors their inputs and outputs. When a component's state changes, Angular checks the component and its child components for changes, ensuring an efficient update of the UI only where necessary. This approach reduces the need for constant checks across the entire application, which would be inefficient. Instead, Angular can identify the parts of the application that need to be updated by propagating changes down the tree from the root. Additionally, Angular makes use of zones, a library that helps track asynchronous operations, allowing for automatic change detection. This means that whenever an event occurs (like a user input or HTTP request), Angular can automatically trigger change detection and update the UI accordingly without necessitating a full application reload or constant monitoring of every user input. Overall, traversing the component tree in a unidirectional flow model provides a systematic and efficient mechanism for change detection, allowing Angular to manage the UI dynamically and responsively based on the underlying data.