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In Angular 7 change detection cycle is being called many times

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0

In my Angular 7 application, I am seeing that ngDoCheck in my AppComponent is being invoked at least 18 times for simple 'div' 'click' event. If not for that 'click' event, I dont see any invokes at all(this was to rule out mousemovement, I running mousemovement outside angular zone). In my click Handler if I invoke stopPropagation on the event, all the invokes are reduced to at least 2. I am struggling to understand what is causing this high no. of change detection cycles. Could this be because of event handlers in parent elements?

I agree that even though ngDoCheck is being invoked, still wont trigger DOM update as long as the input bindings (for onpush) and view bindings are not changed. But still bothers me, why its being invoked so many times.

javascript angular

share|improve this question

edited Mar 24 at 1:27

Anoop Isaac

asked Mar 23 at 17:36

Anoop IsaacAnoop Isaac

678712

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  3
  

  
  
  
  
  
  

  
  
  mouse movements cause a change detection cycle in default change detection, and change detection cycles propagate up and down your component tree. switch to on push detection if you have performance issues. otherwise don't worry about it.
  
  – bryan60
  Mar 23 at 17:39
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  execution of ngDoCheck does not necessarily equate to running of change detection cycle. see this: blog.angularindepth.com/…
  
  – alt255
  Mar 23 at 19:07
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I agree that even though ngDoCheck is being invoked, still wont trigger DOM update as long as the input bindings (for onpush)/view bindings are not changed. But still bothers me, why its being invoked so many times.
  
  – Anoop Isaac
  Mar 24 at 1:25
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  using an empty angular project and binding click in the main component gives me 1 check per click. having mousedown and mouseup as well gives 3 checks. 18 seems like a lot, but without seeing any code it is impossible to tell why that happens. a good way of finding out is to use chromes performance profiler. you can see which check was called by which event, you could also use console.trace() in the ngDoCheck function
  
  – x4rf41
  Mar 24 at 3:20
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  lemme do a console.trace and strip it down to bare minimum code to find out the source of invocation.
  
  – Anoop Isaac
  Mar 25 at 5:23
  

  
  
  
  

add a comment | 

0

In my Angular 7 application, I am seeing that ngDoCheck in my AppComponent is being invoked at least 18 times for simple 'div' 'click' event. If not for that 'click' event, I dont see any invokes at all(this was to rule out mousemovement, I running mousemovement outside angular zone). In my click Handler if I invoke stopPropagation on the event, all the invokes are reduced to at least 2. I am struggling to understand what is causing this high no. of change detection cycles. Could this be because of event handlers in parent elements?

I agree that even though ngDoCheck is being invoked, still wont trigger DOM update as long as the input bindings (for onpush) and view bindings are not changed. But still bothers me, why its being invoked so many times.

javascript angular

share|improve this question

edited Mar 24 at 1:27

Anoop Isaac

asked Mar 23 at 17:36

Anoop IsaacAnoop Isaac

678712

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  mouse movements cause a change detection cycle in default change detection, and change detection cycles propagate up and down your component tree. switch to on push detection if you have performance issues. otherwise don't worry about it.
  
  – bryan60
  Mar 23 at 17:39
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  execution of ngDoCheck does not necessarily equate to running of change detection cycle. see this: blog.angularindepth.com/…
  
  – alt255
  Mar 23 at 19:07
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I agree that even though ngDoCheck is being invoked, still wont trigger DOM update as long as the input bindings (for onpush)/view bindings are not changed. But still bothers me, why its being invoked so many times.
  
  – Anoop Isaac
  Mar 24 at 1:25
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  using an empty angular project and binding click in the main component gives me 1 check per click. having mousedown and mouseup as well gives 3 checks. 18 seems like a lot, but without seeing any code it is impossible to tell why that happens. a good way of finding out is to use chromes performance profiler. you can see which check was called by which event, you could also use console.trace() in the ngDoCheck function
  
  – x4rf41
  Mar 24 at 3:20
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  lemme do a console.trace and strip it down to bare minimum code to find out the source of invocation.
  
  – Anoop Isaac
  Mar 25 at 5:23
  

  
  
  
  

add a comment | 

In my Angular 7 application, I am seeing that ngDoCheck in my AppComponent is being invoked at least 18 times for simple 'div' 'click' event. If not for that 'click' event, I dont see any invokes at all(this was to rule out mousemovement, I running mousemovement outside angular zone). In my click Handler if I invoke stopPropagation on the event, all the invokes are reduced to at least 2. I am struggling to understand what is causing this high no. of change detection cycles. Could this be because of event handlers in parent elements?

I agree that even though ngDoCheck is being invoked, still wont trigger DOM update as long as the input bindings (for onpush) and view bindings are not changed. But still bothers me, why its being invoked so many times.

javascript angular

share|improve this question

edited Mar 24 at 1:27

Anoop Isaac

asked Mar 23 at 17:36

Anoop IsaacAnoop Isaac

678712

javascript angular

javascript angular

share|improve this question

edited Mar 24 at 1:27

Anoop Isaac

asked Mar 23 at 17:36

Anoop IsaacAnoop Isaac

678712

share|improve this question

edited Mar 24 at 1:27

Anoop Isaac

asked Mar 23 at 17:36

Anoop IsaacAnoop Isaac

678712

asked Mar 23 at 17:36

Anoop IsaacAnoop Isaac

678712

asked Mar 23 at 17:36

Anoop IsaacAnoop Isaac

678712