Angular 2+中* ngIf条件中的代码多久会发生一次火灾？

Question

I am curious about how *ngif works:

<img *ngif="isMediaMessage(message) === 'audio'" src="assets/img/audio1" />

1) When I put a console inside the isMediaMessage function, the console prints out indefinitely; I wonder why it does that. Is it because of the digest loop? dirty checking? I am reading up more on these.

2) Should I use less data binding if I want to reduce rendering time?

3) Would you guys say this article is up to date?

This might be related.

Answer 1

This is concerning to the digest loop/detection cycle and the watches on the page.

Every time there is a change in the page and the queue of dirty checking is running then the mechanism of detection is running will reevaluate the ngIf and your code/condition of ngIf will fire.