![How to Enable Lazy Loading (2/4)
Step 2: Create a routing module for lazy loaded module
const routes: Routes = [{
path: '',
component: AdminComponent,
children: [
{ path: '', redirectTo: 'list', pathMatch: 'full' },
{ path: 'list', component: WorkshopListComponent },
{ path: 'new', component: WorkshopEditorComponent },
{ path: 'edit/:id', component: WorkshopEditorComponent },
]
}];
@NgModule({
imports: [ RouterModule.forChild(routes) ],
exports: [ RouterModule ],
})
export class AdminRoutingModule {}
Always use the method forChild when importing the RouterModule
Avoids duplication of services in the child injector](https://image.slidesharecdn.com/angularperformanceslides-170125204649/85/Angular-performance-slides-17-320.jpg)
![How to Enable Lazy Loading (4/4)
Step 4: Use the property loadChildren to lazy load the module
export const routes: Routes = [{
path: 'admin',
loadChildren: 'app/admin/admin.module#AdminModule',
canActivate: [ AuthGuardService ],
}];
@NgModule({
imports: [ RouterModule.forRoot(routes) ],
exports: [ RouterModule ],
})
export class AppRoutingModule {}
Only in the root module use the forRoot method of RouterModule
Never import a lazy loaded in this file, use a string as reference
The path of loadChildren is not relative to the file, but to the index.html file
(Show routes in the IDE and URL structure of the app)](https://image.slidesharecdn.com/angularperformanceslides-170125204649/85/Angular-performance-slides-19-320.jpg)
![Enable Preloading
Define the property preloadingStrategy in the root module routing
import { PreloadAllModules } from '@angular/router';
export const routes: Routes = [ ... ];
@NgModule({
imports: [
RouterModule.forRoot(routes, {
preloadingStrategy: PreloadAllModules
})
],
exports: [ RouterModule ],
})
export class AppRoutingModule {}](https://image.slidesharecdn.com/angularperformanceslides-170125204649/85/Angular-performance-slides-21-320.jpg)
![Summary
What to do?
Apply the OnPush change detection on every component*
Never mutate an object or array, always create a a new reference ( )blog
// Don't
let addPerson = (person: Person): void => {
people.push(person);
};
// Do
let addPerson = (people: Person[], person: Person): Person[] => {
return [ ...people, person ];
};
Benefits:
Fewer checks of your components during Change Detection
Improved overall app performance](https://image.slidesharecdn.com/angularperformanceslides-170125204649/85/Angular-performance-slides-28-320.jpg)
![What Causes Memory Leaks in Angular?
Main Source => Subscriptions to observables never closed
@Injectable()
export class WorkshopService {
getAll(): Observable<Workshop[]> { ... }
}
@Component({
selector: 'rio-workshop-list',
template: `
<div *ngFor="let workshop of workshops">
{{ workshop.title }}
</div>`
})
export class WorkshopListComponent implements OnInit {
...
ngOnInit() {
this.service.getAll().subscribe(workshops => this.workshops = workshops);
}
}](https://image.slidesharecdn.com/angularperformanceslides-170125204649/85/Angular-performance-slides-31-320.jpg)
Angular performance slides
- 1. Small computers, big performance: Optimize your Angular
- 3. Agenda 1. Ahead of Time Compilation 2. Lazy Loading 3. Change Detection 4. Memory Leaks 5. Server Side Rendering
- 4. Rangle Academy Goal and Structure: Program to share knowledge within the company It follows a "workshop" structure Usually 2 hours long Covers hard and soft skills Some workshops available: Webpack React React Native Google Analytics Unit Testing Introduction to Payment Gateways Continuous Delivery to Production Conflict Management
- 5. About the Demo App Characteristics: Built using Angular 2.4.1 Uses Angular CLI beta-26 Redux store with ngrx Tachyons for CSS Server side rendering with Universal All the numbers shown are based on: Low end device emulation (5x slowdown) Good 3G connection emulation
- 6. Ahead of Time Compilation (AoT)
- 7. Compilation Modes Just in Time Compilation (JiT): Compilation performed in the browser at run time Bigger bundle size (includes the compiler) Takes longer to boot the app $ ng serve --prod Ahead of Time Compilation (AoT): Compilation performed in the server at build time Smaller bundle size (doesn't include the compiler) The app boots faster $ ng serve --prod --aot
- 10. JiT vs AoT in Demo App (Prod + Gzip) CSS files are included in the "other js files" File Size (JiT) Size (AoT) main.bundle.js 6.4 KB 23.9 KB vendor.bundle.js 255 KB 158 KB other js files 48.7 KB 49.6 KB Total Download 306 KB 231.5 KB AoT goals (from the ):docs Faster rendering => Components already compiled Fewer async request => Inline external HTML and CSS Smaller bundle size => No compiler shipped Detect template errors => Because they can Better security => Prevents script injection attack
- 11. Boot Time Comparison Event Time (JiT) Time (AoT) DOM Content Loaded 5.44 s 3.25 s Load 5.46 s 3.27 s FMP 5.49 s 3.30 s DOM Content Loaded: The browser has finished parsing the DOM jQuery nostalgia => $(document).ready() Load: All the assets has been downloaded First Meaningful Paint (FMP): When the user is able to see the app "live" for the first time (Show browser profile for both modes)
- 12. Lazy Loading
- 13. What is Lazy Loading? Ability to load modules on demand => Useful to reduce the app startup time (Compare branches no-lazy-loading vs normal-lazy-loading )
- 14. Bundle Sizes Comparison (Prod + AoT) File Size (No LL) Size (LL) main.bundle.js 23.9 KB 17.4 KB vendor.bundle.js 158 KB 158 KB other js files 49.6 KB 49.6 KB Initial Download 231.5 KB 225 KB 0.chunk.js - 9.1 KB Total Download 231.5 KB 234.1 KB Webpack creates a "chunk" for every lazy loaded module The file 0.chunk.js is loaded when the user navigates to admin The initial download size is smaller with LL The total size over time is bigger with LL because of Webpack async loading The effect of LL start to be noticeable when the app grows
- 15. Boot Time Comparison (Prod + AoT) Event Time (No LL) Time (LL) DOM Content Loaded 3.25 s 3.11 s Load 3.27 s 3.25 s FMP 3.30 s 3.16 s Not much difference for an small app Just one lazy loaded module with a couple of components The impact is noticeable for big apps
- 16. How to Enable Lazy Loading? (1/4) Step 1: Organize your code into modules $ tree src/app -L 1 src/app ├── admin/ ├── app-routing.module.ts ├── app.component.ts ├── app.module.ts ├── core/ ├── public/ └── shared/ CoreModule provides all the services and the Redux store SharedModule provides all the reusable components, directives or pipes PublicModule provides the components and routing of the public section of the app AdminModule provides the components and routing of the private section of the app AppModule root module (Show modules in the IDE)
- 17. How to Enable Lazy Loading (2/4) Step 2: Create a routing module for lazy loaded module const routes: Routes = [{ path: '', component: AdminComponent, children: [ { path: '', redirectTo: 'list', pathMatch: 'full' }, { path: 'list', component: WorkshopListComponent }, { path: 'new', component: WorkshopEditorComponent }, { path: 'edit/:id', component: WorkshopEditorComponent }, ] }]; @NgModule({ imports: [ RouterModule.forChild(routes) ], exports: [ RouterModule ], }) export class AdminRoutingModule {} Always use the method forChild when importing the RouterModule Avoids duplication of services in the child injector
- 18. How to Enable Lazy Loading (3/4) Step 3: Define a child <router-outlet> to render child routes @Component({ selector: 'rio-admin', template: ` <nav> <a routerLink="./list">List Workshops</a> <a routerLink="./new">Create Workshop</a> </nav> <router-outlet></router-outlet> `, }) export class AdminComponent {}
- 19. How to Enable Lazy Loading (4/4) Step 4: Use the property loadChildren to lazy load the module export const routes: Routes = [{ path: 'admin', loadChildren: 'app/admin/admin.module#AdminModule', canActivate: [ AuthGuardService ], }]; @NgModule({ imports: [ RouterModule.forRoot(routes) ], exports: [ RouterModule ], }) export class AppRoutingModule {} Only in the root module use the forRoot method of RouterModule Never import a lazy loaded in this file, use a string as reference The path of loadChildren is not relative to the file, but to the index.html file (Show routes in the IDE and URL structure of the app)
- 20. Preloading (Compare branches normal-lazy-loading vs master )
- 21. Enable Preloading Define the property preloadingStrategy in the root module routing import { PreloadAllModules } from '@angular/router'; export const routes: Routes = [ ... ]; @NgModule({ imports: [ RouterModule.forRoot(routes, { preloadingStrategy: PreloadAllModules }) ], exports: [ RouterModule ], }) export class AppRoutingModule {}
- 22. Change Detection
- 23. What's Change Detection (CD)? It's a mechanism to keep our "models" in sync with our "views" Change detection is fired when... The user interacts with the app (click, submit, etc.) An async event is completed (setTimeout, promise, observable) When CD is fired, Angular will check every component starting from the top once.
- 24. Change Detection Strategy: OnPush Angular offers 2 strategies: Default: Check the entire component when CD is fired OnPush: Check only relevant subtrees when CD is fired OnPush Requirements: Component inputs ( @Input ) need to be immutable objects @Component({ selector: 'rio-workshop', templateUrl: './workshop.component.html', changeDetection: ChangeDetectionStrategy.OnPush }) export class WorkshopComponent { @Input() workshop: Workshop; @Input() isSummary = false; } View Example
- 25. Example: The Component Tree
- 28. Summary What to do? Apply the OnPush change detection on every component* Never mutate an object or array, always create a a new reference ( )blog // Don't let addPerson = (person: Person): void => { people.push(person); }; // Do let addPerson = (people: Person[], person: Person): Person[] => { return [ ...people, person ]; }; Benefits: Fewer checks of your components during Change Detection Improved overall app performance
- 29. Memory Leaks
- 30. What's Memory Leak? The increase of memory usage over time
- 31. What Causes Memory Leaks in Angular? Main Source => Subscriptions to observables never closed @Injectable() export class WorkshopService { getAll(): Observable<Workshop[]> { ... } } @Component({ selector: 'rio-workshop-list', template: ` <div *ngFor="let workshop of workshops"> {{ workshop.title }} </div>` }) export class WorkshopListComponent implements OnInit { ... ngOnInit() { this.service.getAll().subscribe(workshops => this.workshops = workshops); } }
- 32. Manually Closing Connections Before the element is destroyed, close the connection @Component({ selector: 'rio-workshop-list', template: ` <div *ngFor="let workshop of workshops"> {{ workshop.title }} </div>` }) export class WorkshopListComponent implements OnInit, OnDestroy { ... ngOnInit() { this.subscription = this.service.getAll() .subscribe(workshops => this.workshops = workshops); } ngOnDestroy() { this.subscription.unsubscribe(); } }
- 33. The async Pipe It closes the connection automatically when the component is destroyed @Component({ selector: 'rio-workshop-list', template: ` <div *ngFor="let workshop of workshops$ | async"> {{ workshop.title }} </div>` }) export class WorkshopListComponent implements OnInit { ngOnInit() { this.workshops$ = this.service.getAll(); } } This is the recommended way of dealing with Observables in your template!
- 34. The Http Service Every method of the http services ( get , post , etc.) returns an observable Those observables emit only one value and the connection is closed automatically They won't cause memory leak issues @Component({ selector: 'rio-workshop-list', template: ` <div *ngFor="let workshop of workshops"> {{ workshop.title }} </div>` }) export class WorkshopListComponent implements OnInit { ... ngOnInit() { this.http.get('some-url') .map(data => data.json()) .subscribe(workshops => this.workshops = workshops); } }
- 35. Emit a Limited Number of Values RxJs provides operators to close the connection automatically Examples: first() and take(n) This won't cause memory leak issues even if getAll emits multiple values @Component({ selector: 'rio-workshop-list', template: ` <div *ngFor="let workshop of workshops"> {{ workshop.title }} </div>` }) export class WorkshopListComponent implements OnInit { ngOnInit() { this.service.getAll().first() .subscribe(workshops => this.workshops = workshops); } }
- 37. Angular Universal Provides the ability to pre-render your application on the server Much faster time to first paint Enables better SEO Enables content preview on social networks Fallback support for older browsers Use the as the base of your applicationuniversal-starter
- 38. What's Included Suite of polyfills for the server Server rendering layer Preboot - replays your user's interactions after Angular has bootstrapped State Rehydration - Don't lose your place when the application loads
- 39. Boot Time Comparison (Client vs Server) Both environments include previous AoT and Lazy Loading enhancements Event Time (Client) Time (Server) DOM Content Loaded 3.11 s 411 ms Load 3.25 s 2.88 s FMP 3.16 s ~440 ms *Times are on mobile over 3G
- 40. Universal Caveats Cannot directly access the DOM constructor(element: ElementRef, renderer: Renderer) { renderer.setElementStyle(element.nativeElement, ‘font-size’, ‘x-large’); } Current solutions only cover Express and ASP.NET servers Project will be migrated into the core Angular repo for v4
- 41. Summary
- 42. Performance Changes Event JiT AoT Lazy Loading SSR DOM Content Loaded 5.44 s 3.25 s 3.11 s 411 ms Load 5.46 s 3.27 s 3.25 s 2.88 s FMP 5.46 s 3.30 s 3.16 s ~440 ms % Improvement (FMP) 39.6% 4.3% 86.1% *Times are on mobile over 3G