Скачать или смотреть Learn Angular 19 : 🔥 Master ngDoCheck() Life cycle hook method 🔥 | Real World Example | Episode 10

In this video, we will discuss about the ngDoCheck() life cycle hook method in angular 19

Introduction to ngDoCheck
ngDoCheck is a lifecycle hook provided by Angular, called during every change detection run.
It allows developers to implement custom change detection logic.
Signature : ngDoCheck(): void
This method is invoked every time Angular checks for changes in the component — whether or not anything has changed.

Why and When to Use ngDoCheck?
Angular provides default change detection with ngOnChanges, which works well for inputs. But ngDoCheck gives you finer control, especially when:
1. You need to detect changes not handled by Angular’s default detection.
2. You're using mutable objects/arrays, and their internal values change without changing the reference.
3. You want to track custom logic on every change detection cycle.
ngOnChanges vs. ngDoCheck?
Feature
ngOnChanges
ngDoCheck
Trigger
When @Input property changes
Every change detection cycle
Granularity
Detects new input reference
Can inspect object deeply
Usage
Simple use cases
Complex, custom detection
Performance
Efficient
Can be expensive if overused

Performance Considerations?
ngDoCheck runs frequently — potentially multiple times per second.
Best Practices:
1. Avoid heavy computation in ngDoCheck.
2. Use it only when needed.
3. Consider KeyValueDiffers or IterableDiffers for better performance in tracking changes in objects and arrays.


Summary for the Lecture

Key Points to Highlight:
ngDoCheck gives full control over change detection.
Use it when Angular's default mechanisms (like ngOnChanges) are not sufficient.
Be mindful of performance.
Consider built-in differ helpers for complex objects/arrays.