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In Angular, you can **create a custom change detection strategy**, but this is **rarely needed**, since the standard strategies (`Default` and `OnPush`) cover most cases. The basic idea is to use the `ChangeDetectorRef` interface and control when Angular checks the component.

## Main approaches

1. **Using** `ChangeDetectorRef` **inside the component**

- You can manually **trigger a change check**.

```ts
import { Component, ChangeDetectorRef } from '@angular/core';

@Component({
  selector: 'app-my',
  template: '{{ counter }}'
})
export class MyComponent {
  counter = 0;

constructor(private cd: ChangeDetectorRef) {}

increment() {
    this.counter++;
    this.cd.detectChanges(); // manually runs the change check
  }
}
```

- Here you **control when the check happens**, instead of relying on Angular's automatic trigger.

2. **Using** `detach()` **and** `reattach()`

- You can **turn off change detection** for the component entirely and enable it only on a specific event.

```ts
ngOnInit() {
  this.cd.detach(); // the component is no longer checked automatically
}

update() {
  this.counter++;
  this.cd.reattach();
  this.cd.detectChanges();
  this.cd.detach();
}
```

- This lets you **implement your "own strategy"**, where the check runs only according to your own rules.

3. **Extending the built-in mechanism**

- Angular does not provide a direct way to register a completely new strategy (`ChangeDetectionStrategy` is an enum), but through `ChangeDetectorRef` and manual control you can simulate any logic.

In other words, **a custom strategy is implemented through manual control of change detection via** `ChangeDetectorRef`, turning off automatic tracking and calling `detectChanges()` only when needed.

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