Christian Liebel @christianliebel Consultant Angular-Performance: So zünden Sie den Turbo Thinktecture Webinar 

Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Agenda Change Detection & NgZone Change Detection Strategies Lazy Loading Service Workers 

Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Agenda Change Detection & NgZone Change Detection Strategies Lazy Loading Service Workers 

Reduce required computations during runtime - calculations - painting - layouting - detecting changes Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Runtime Performance 

Hi Angular! Basics // app.component.html

Hi {{ title }}!

// app.component.ts @Component({ /* … */ }) export class AppComponent { title = 'Angular'; } Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Change Detection 

Basics // app.component.html

Hi {{ title }}!

Update // app.component.ts @Component({ /* … */ }) export class AppComponent { title = 'Angular'; update() { this.title = 'Foo'; } } Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Change Detection Hi Foo! Hi Angular! Update 

Component Tree AppComponent NavComponent ContentComponent ListComponent Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Change Detection 

Change Detector Tree AppComponent NavComponent ContentComponent ListComponent Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Change Detection AppComponent CD NavComponent CD ContentComponent CD ListComponent CD CHANGE 

Per default, each change in your application leads to… - A single CD cycle - From top to bottom (all components) - Unidirectional (no cycles allowed) Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Change Detection DEMO 

Findings Reduce duration of a change detection cycle - Reduce amount of bindings (e.g. grids: virtual scrolling via CDK) - Avoid binding to (computationally intensive) getters or functions Keep CD cycle < 16 ms! Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Change Detection 

Profiling // main.ts platformBrowserDynamic().bootstrapModule(AppModule).then(module => enableDebugTools(module.injector.get(ApplicationRef).components[0])); Execute ng.profiler.timeChangeDetection() to measure the duration of a change detection run (500ms or 5 change detection cycles) Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Change Detection DEMO 

How to detect a change? AppComponent NavComponent ContentComponent ListComponent Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Zone.js AppComponent CD NavComponent CD ContentComponent CD ListComponent CD CHANGE 

A look at Angular’s dependencies "dependencies": { "@angular/common": "~11.0.1", "rxjs": "~6.6.0", "tslib": "^2.0.0", "zone.js": "~0.10.2" }, Zone.js Thinktecture Webinar Angular Performance: So zünden Sie den Turbo 

Overview Provided by the Angular team Open-source https://github.com/angular/zone.js 1. Provides an execution context for asynchronous JavaScript 2. A meta-monkey patch Zone.js Thinktecture Webinar Angular Performance: So zünden Sie den Turbo 

Execution Context Oversimplified Zone.run(main); onZoneEnter(); function main() { a(); setTimeout(b, 0); c(); } onZoneLeave(); Zone.js const orig = window.setTimeout; window.setTimeout = (c, t) => { orig(() => { onZoneEnter(); c(); onZoneLeave(); }, t); }; Thinktecture Webinar Angular Performance: So zünden Sie den Turbo 

A Meta-Monkey Patch Zone.js setTimeout setInterval geolocation.getCurrentPosition XMLHttpRequest PromiseRejectionEvent requestAnimationFrame click focus mousemove addEventListener Thinktecture Webinar Angular Performance: So zünden Sie den Turbo 

NgZone Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Zone.js current (global) zone NgZone Angular boot 

NgZone NgZone catches asynchronous operations from the Angular app When no tasks are remaining for the current VM turn, the NgZone will trigger a change detection cycle (tick) Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Zone.js NgZone setTimeout setInterval onclick Detect changes Detect changes Detect changes 

Change Detection Trigger https://github.com/angular/angular/blob/master/packages/core/src/application_ref.ts Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Zone.js NgZone.onMicrotaskEmpty ApplicationRef.tick() view1.detectChanges() view2.detectChanges() viewN.detectChanges() 

Common Pitfalls Long CD cycles in combination with high-frequency events - mousemove - scroll - requestAnimationFrame - setInterval with short intervals (clocks!) Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Zone.js DEMO 

NgZone Zone.js current (global) zone NgZone rAF Detect changes rAF Detect changes rAF Detect changes rAF Detect changes Thinktecture Webinar Angular Performance: So zünden Sie den Turbo 

NgZone Opt-Out constructor (ngZone: NgZone) { ngZone.runOutsideAngular(() => { // runs outside Angular zone, for performance-critical code ngZone.run(() => { // runs inside Angular zone, for updating view afterwards }); }); } Zone.js Thinktecture Webinar Angular Performance: So zünden Sie den Turbo ! View and model can get out of sync! DEMO 

NgZone Zone.js current (global) zone NgZone rAF rAF rAF rAF Thinktecture Webinar Angular Performance: So zünden Sie den Turbo 

Disable Patches (polyfills.ts) (window as any).__Zone_disable_requestAnimationFrame = true; // disable patch requestAnimationFrame (window as any).__Zone_disable_on_property = true; // disable patch onProperty such as onclick (window as any).__zone_symbol__UNPATCHED_EVENTS = ['scroll', 'mousemove']; // disable patch specified eventNames Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Zone.js ! View and model can get out of sync! 

Event Coalescing // main.ts platformBrowserDynamic().bootstrapModule(AppModule, { ngZoneEventCoalescing: true }); Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Zone.js ! App behavior may change! CHANGE CHANGE Coalescing 

Disable Zone (= disable async change detection!) platformBrowserDynamic().bootstrapModule(AppModule, { ngZone: 'noop' }); constructor(applicationRef: ApplicationRef) { applicationRef.tick(); // trigger CD yourself } Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Zone.js ! View and model can get out of sync! 

Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Agenda Change Detection & NgZone Change Detection Strategies Lazy Loading Service Workers 

Overview Default Uses Zone.js for detecting changes and updates bindings OnPush Restricts change detection to changes of @Input parameters Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Change Detection Strategies AppComponent CD NavComponent CD ContentComponent CD ListComponent CD AppComponent CD NavComponent CD ContentComponent CD ListComponent CD OnPush 

OnPush @Component({ selector: 'my-component', template: '{{ foo }}', changeDetection: ChangeDetectionStrategy.OnPush }) export class MyComponent { @Input() public foo: string; } Change detection only reacts to changes of @Input parameters Angular compares the values passed to an @Input parameter (newValue === oldValue). If you are passing objects, make sure to pass in new instances! Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Change Detection Strategies ! View and model can get out of sync! 

// app.component.ts @Component({ changeDetection: ChangeDetectionStrategy.OnPush }) /* … */ ngOnInit() { requestAnimationFrame(() => this.ngOnInit()); // this._ngZone.runOutsideAngular(() => request…); } Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Change Detection Strategies DEMO 

OnPush & Detecting Changes What to do if a component changes unrelated to an @Input parameter? constructor(private dataService: DataService) {} ngOnInit() { this.dataService.updates$ .subscribe(newData => this.data = newData); // no update! } Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Change Detector 

markForCheck() Explicitly marks a component as dirty/changed (when using OnPush) Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Change Detector AppComponent CD NavComponent CD ContentComponent CD ListComponent CD DIRTY AppComponent CD NavComponent CD ContentComponent CD ListComponent CD OnPush 

markForCheck() constructor(private dataService: DataService, private cdRef: ChangeDetectorRef) {} ngOnInit() { this.dataService.updates$.subscribe(newData => { this.data = newData; this.cdRef.markForCheck(); }); } Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Change Detector 

Overview Takes observables, promises or synchronous values {{ data$ | async }} Waits for the observable to emit/promise to resolve and then displays the value Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Async Pipe 

Advantages For observables: - Async Pipe subscribes for you - Async Pipe takes care of unsubscribing from the observable - Async Pipe calls markForCheck() for each update – perfect match for OnPush! https://github.com/angular/angular/blob/master/packages/common/src/pipes/async_pipe.ts Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Async Pipe 

Simplifying OnPush constructor(private dataService: DataService, private cdRef: ChangeDetectorRef) {} ngOnInit() { this.dataService.updates$.subscribe(newData => { this.data = newData; this.cdRef.markForCheck(); }); } Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Async Pipe 

Simplifying OnPush // component.ts data$: Observable; constructor(dataService: DataService) { this.data$ = this.dataService.updates$; } // component.html {{ data$ | async }} Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Async Pipe DEMO 

Detaching Components changeDetector.detach(); changeDetector.reattach(); Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Change Detector AppComponent CD NavComponent CD ContentComponent CD ListComponent CD AppComponent CD NavComponent CD ContentComponent CD ListComponent CD ! View and model can get out of sync! 

Findings Reduce amount of change detection cycles - Disable Zone.js (not a good idea in most cases) - Coalesce CD cycles (might change behavior of existing apps) - Opt-out of NgZone (for operations that should not affect bindings) - Disable Zone.js patches (in case you can’t opt-out, e.g. 3rd party libs) - ChangeDetectionStrategy.OnPush (good default, but be careful) - Local change detection via ChangeDetectorRef (for the few components that do not have to respond to changes from outside) Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Change Detector 

- Reduce initial load (size & computation) - Reduce perceived loading time - Prevent downloading the same resource again Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Load Time Performance 

Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Agenda Change Detection & NgZone Change Detection Strategies Lazy Loading Service Workers 

Overview Angular router supports lazy loading components transparently Lazy loaded components are not delivered to/loaded by the client on boot, but on purpose Reduces load & perceived loading time Lazy Loading Thinktecture Webinar Angular Performance: So zünden Sie den Turbo 

Architecture Lazy Loading is module-based Module is resolved via a dynamic import: import('./feature.module').then(m => m.FeatureModule) Routing is delegated to the feature module called Lazy Loading Thinktecture Webinar Angular Performance: So zünden Sie den Turbo 

Overview const ROUTES: Routes = [{ path: 'admin', loadChildren: () => import('app/admin/admin.module') .then(a => a.AdminModule) }]; Lazy Loading Thinktecture Webinar Angular Performance: So zünden Sie den Turbo DEMO 

Configuring Lazy Loading NoPreloading - does not preload any route by default - advantage: low size footprint - disadvantage: takes some time after clicking a link to the lazy-loaded module, not offline capable PreloadAllModules - automatically preloads all modules after the application has launched (still better loading time!) - advantage: lazy-loaded modules now load instant (also on the first click), offline capable - disadvantage: higher footprint Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Preloading Strategies 

Configuring Lazy Loading @NgModule({ imports: [RouterModule.forRoot(routes, { preloadingStrategy: PreloadAllModules, })], exports: [RouterModule] }) export class AppRoutingModule { } Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Preloading Strategies 

Custom Strategy It’s also possible to provide a custom strategy - when modules belong to each other - it’s expected that the user will access a certain module next (e.g. checkout after cart module) Developer can decide which modules should be preloaded on a navigation event Developer gets access to the modules which have not been preloaded yet Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Preloading Strategies 

Unrelated To Routes Angular CLI generates bundles for all import()s and transparently downloads them when the function is invoked. function onClick() { import('./heavy-bundle').then(bundle => bundle.compute()); } Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Lazy Loading 

Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Agenda Change Detection & NgZone Change Detection Strategies Lazy Loading Service Workers 

Idea: Never load the same resource twice Download resources once and store them in a local cache The next time the user wants to open the application, load the contents from there Makes your application sources offline-capable Significantly improves loading time Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Service Worker 

Key Technology Service Worker Service Worker Internet Website HTML/JS Cache fetch Thinktecture Webinar Angular Performance: So zünden Sie den Turbo 

Commands ng add @angular/pwa ng build --prod cd dist/perf-demo npx lite-server Service Worker Thinktecture Webinar Angular Performance: So zünden Sie den Turbo DEMO 

Findings – Prevent downloading the same resource twice by using the Service Worker – Postpone loading less frequently used parts of your application by leveraging lazy loading Angular Performance: So zünden Sie den Turbo Thinktecture Webinar Load-Time Performance 

Thank you for your kind attention! Christian Liebel @christianliebel [email protected]