Angular Interview Practice

What happens to impure pipes in terms of Angular's performance?

1. They optimize performance

2. They can negatively impact performance

3. They work faster than pure pipes

4. They are less frequently executed

The correct answer is: They can negatively impact performance

Impure pipes can negatively impact performance because they are re-evaluated on every change detection cycle. In Angular, there are two types of pipes: pure and impure. Pure pipes only re-evaluate when the input reference changes, which is more efficient as they minimize the number of times Angular needs to execute the pipe during change detection. In contrast, impure pipes can be recalculated with every single change detection run, regardless of whether their input has changed. This means if your application has frequent change detection cycles, impure pipes can lead to decreased performance because they require more computational resources. This makes their use less favorable when performance is a concern, especially in applications that handle large amounts of data or have heavy UI interactions. Therefore, recognizing how impure pipes operate is crucial for optimizing Angular applications effectively.