Why does Angular 2 have better performance than Angular 1?

Question

Wonderful developers, I need a little help clarifying why Angular 2 is more performant than Angular 1?

After searching the web, I came up with this relevant explanation from Er Shahbaz Sharif in a Quora discussion:

Angular 2 is using Hierarchical Dependency Injection system which is major performance booster. 
Angular 2 implements unidirectional tree based change detection which again increases performance . 
As per ng-conf meetup, angular 2 is 5 times faster as compared to angular 1

Other explanations in the same discussion seem to hover around this as well.

Could somebody please clarify for me why those 2 factors (and others, if any) help boost the performance of Angular 2? Thanks so much..

Answer 1

Angular2 - doesn't do deep object compairson. If items are added/removed to/from an array, change detection won't detect it. The same for object properties as long as they are not directly bound from the view.

• Two-way binding is split into propagating detected changes from root to leaves only.

• Changes from child to parent are only propagated by explicit events (outputs), only to direct parents.

• ChangeDetectionStrategy.OnPush doesn't run change detection for components when no input values have changes. This prunes subtrees of components where change detection isn't run at all.

• The code (especially the change detection code) is written in a way that it can be optimized as much as possible by the JS VMs.

https://www.quora.com/What-is-the-difference-between-angularjs-and-angular2

Answer 2

One of the reasons for performance is the possibility of the existence of change detection loops.

• Angular1 hamstrung its performance with how it polled state. During every digest cycle, the framework checks if any of hundreds or thousands of values in your app changed.
• Angular 2 will allow the developer to provide some guarantees to the change detection mechanism to avoid scanning parts of the component tree. For more details, you can find more at here.