No,Category,Guideline,Description,Do,Don't,Code Good,Code Bad,Severity,Docs URL 1,Components,Use standalone components,Angular 17+ default; no NgModule needed,Standalone components for all new code,NgModule-based components for new projects,"@Component({ standalone: true imports: [CommonModule] })","@NgModule({ declarations: [MyComp] })",High,https://angular.dev/guide/components/importing 2,Components,Use signals for state,Signals are Angular's reactive primitive for fine-grained reactivity,Signals for component state over class properties,Mutable class properties without signals,"count = signal(0); increment() { this.count.update(v => v + 1) }","count = 0; increment() { this.count++ }",High,https://angular.dev/guide/signals 3,Components,Use @if/@for/@switch control flow,Built-in control flow syntax replaces *ngIf/*ngFor directives,@if and @for in templates,*ngIf and *ngFor structural directives,"@if (isLoggedIn) { } @else { }","
",High,https://angular.dev/guide/templates/control-flow 4,Components,Use input() and output() signals,Signal-based inputs/outputs replace @Input()/@Output() decorators,input() and output() for component API,@Input() and @Output() decorators,"name = input(); clicked = output()","@Input() name: string; @Output() clicked = new EventEmitter()",High,https://angular.dev/guide/components/inputs 5,Components,Use content projection,ng-content for flexible component composition,ng-content with select for named slots,Rigid templates that can't be customized," ","
{{ title }}
",Medium,https://angular.dev/guide/components/content-projection 6,Components,Keep components small,Single responsibility; components should do one thing,Extract sub-components when template exceeds 50 lines,Monolithic components handling multiple concerns," ",One 300-line component template,Medium,https://angular.dev/guide/components 7,Components,Use OnPush change detection,Reduces re-renders by only checking on input changes or signal updates,OnPush for all components,Default change detection strategy,"changeDetection: ChangeDetectionStrategy.OnPush","changeDetection: ChangeDetectionStrategy.Default",High,https://angular.dev/guide/components/lifecycle 8,Components,Avoid direct DOM manipulation,Use renderer or ElementRef sparingly; prefer template bindings,Template bindings and Angular directives,Direct document.querySelector or innerHTML,"[class.active]=""isActive""","this.el.nativeElement.classList.add('active')",High,https://angular.dev/guide/components/host-elements 9,Routing,Lazy load feature routes,Load route chunks on demand to reduce initial bundle,loadComponent() for all feature routes,Eager-loaded routes in app config,"{ path: 'admin' loadComponent: () => import('./admin/admin.component') }","{ path: 'admin' component: AdminComponent }",High,https://angular.dev/guide/routing/lazy-loading 10,Routing,Use route guards with functional API,Protect routes with canActivate/canMatch functional guards,Functional guards returning boolean or UrlTree,Class-based guards with CanActivate interface,"canActivate: [() => inject(AuthService).isLoggedIn()]","canActivate: [AuthGuard]",High,https://angular.dev/guide/routing/common-router-tasks#preventing-unauthorized-access 11,Routing,Use route resolvers for data,Pre-fetch data before route activation using resolve,ResolveFn for route data,Fetching data in ngOnInit causing flash of empty state,"resolve: { user: () => inject(UserService).getUser() }",Fetch in ngOnInit with loading state flickering,Medium,https://angular.dev/guide/routing/common-router-tasks#resolve 12,Routing,Type route params with inject,Use inject(ActivatedRoute) with signals or toSignal,Typed route params via ActivatedRoute,Untyped route.snapshot.params string access,"const id = toSignal(route.paramMap.pipe(map(p => p.get('id'))))","const id = this.route.snapshot.params['id']",Medium,https://angular.dev/api/router/ActivatedRoute 13,Routing,Use nested routes for layouts,Compose shared layouts using router-outlet nesting,Nested routes with shared layout components,Duplicating layout code across routes,"{ path: 'app' component: ShellComponent children: [...] }",Duplicate header/sidebar in each route component,Medium,https://angular.dev/guide/routing/router-tutorial-toh#child-route-configuration 14,Routing,Configure preloading strategies,Preload lazy modules in background after initial load,PreloadAllModules or custom strategy,No preloading causing delayed navigation,"provideRouter(routes withPreloading(PreloadAllModules))","provideRouter(routes)",Low,https://angular.dev/api/router/PreloadAllModules 15,State,Use signals for local state,Signals provide synchronous reactive state without RxJS overhead,signal() for component-local reactive state,BehaviorSubject for simple local state,"const items = signal([]); addItem(i: Item) { this.items.update(arr => [...arr i]) }","items$ = new BehaviorSubject([])",High,https://angular.dev/guide/signals 16,State,Use computed() for derived state,Lazily evaluated derived values that update when dependencies change,computed() for values derived from other signals,Duplicated state or manual sync,"readonly total = computed(() => this.items().reduce((s i) => s + i.price 0))","this.total = this.items.reduce(...) // called manually",High,https://angular.dev/guide/signals#computed-signals 17,State,Use effect() carefully,Effects run side effects when signals change; avoid overuse,effect() for side effects like logging or localStorage sync,effect() for deriving state (use computed instead),"effect(() => localStorage.setItem('cart' JSON.stringify(this.cart())))","effect(() => { this.total.set(this.items().length) })",Medium,https://angular.dev/guide/signals#effects 18,State,Use NgRx Signal Store for complex state,NgRx Signal Store is the modern lightweight state management for Angular,@ngrx/signals SignalStore for feature state,Full NgRx reducer/action/effect boilerplate for simple state,"const Store = signalStore(withState({ count: 0 }) withMethods(s => ({ increment: () => patchState(s { count: s.count() + 1 }) })))","createReducer(on(increment state => ({ ...state count: state.count + 1 })))",Medium,https://ngrx.io/guide/signals 19,State,Inject services for shared state,Services with signals share state across components without a store,Injectable service with signals for cross-component state,Prop drilling or @Input chains for shared state,"@Injectable({ providedIn: 'root' }) class CartService { items = signal([]) }","@Input() cartItems passed through 4 component levels",Medium,https://angular.dev/guide/di/creating-injectable-service 20,State,Avoid mixing RxJS and signals unnecessarily,Use toSignal() to bridge RxJS into signal world at the boundary,toSignal() to convert observable to signal at component edge,Subscribing in components and storing in signal manually,"readonly user = toSignal(this.userService.user$)","this.userService.user$.subscribe(u => this.user.set(u))",Medium,https://angular.dev/guide/rxjs-interop 21,Forms,Use typed reactive forms,FormGroup/FormControl with explicit generics for compile-time safety,FormBuilder with typed controls,Untyped FormControl or any casts,"fb.group({ email: fb.control('') password: fb.control('') })","new FormGroup({ email: new FormControl(null) })",High,https://angular.dev/guide/forms/typed-forms 22,Forms,Use reactive forms over template-driven,Reactive forms scale better and are fully testable,ReactiveFormsModule for all non-trivial forms,FormsModule with ngModel for complex forms,"","",Medium,https://angular.dev/guide/forms/reactive-forms 23,Forms,Write custom validators as functions,Functional validators are composable and tree-shakeable,ValidatorFn functions for custom validation,Class-based validators implementing Validator interface,"const noSpaces: ValidatorFn = ctrl => ctrl.value?.includes(' ') ? { noSpaces: true } : null","class NoSpacesValidator implements Validator { validate(c) {} }",Medium,https://angular.dev/guide/forms/form-validation#custom-validators 24,Forms,Use updateOn for performance,Control when validation runs to avoid per-keystroke validation overhead,updateOn: 'blur' or 'submit' for expensive validators,Default updateOn: 'change' for async validators,"fb.control('' { updateOn: 'blur' validators: [Validators.email] })","fb.control('' [Validators.email]) // validates on every key",Low,https://angular.dev/api/forms/AbstractControl#updateOn 25,Forms,Use FormArray for dynamic fields,FormArray manages variable-length lists of controls,FormArray for add/remove field scenarios,Manually tracking index-based controls,"get items(): FormArray { return this.form.get('items') as FormArray }","items: [FormControl] managed outside form",Medium,https://angular.dev/guide/forms/reactive-forms#using-the-formarray-class 26,Forms,Display validation errors clearly,Use form control touched and dirty states to show errors at the right time,Show errors after field is touched,Show all errors on page load,"@if (email.invalid && email.touched) { Invalid email }","@if (email.invalid) { Invalid email }",Medium,https://angular.dev/guide/forms/form-validation 27,Performance,Apply OnPush to all components,OnPush + signals eliminates most unnecessary change detection cycles,OnPush change detection everywhere,Default strategy which checks entire tree on every event,changeDetection: ChangeDetectionStrategy.OnPush,changeDetection: ChangeDetectionStrategy.Default,High,https://angular.dev/best-practices/skipping-component-subtrees 28,Performance,Use trackBy in @for blocks,Stable identity for list items prevents full DOM re-creation on change,track item.id in @for,"@for (item of items; track item.id) {
  • {{ item.name }}
    • }","@for (item of items; track $index) {
  • {{ item.name }}
    • }",High,https://angular.dev/guide/templates/control-flow#track-and-identity 29,Performance,Use @defer for below-the-fold content,Defer blocks lazy-load components when they enter the viewport,@defer with on viewport for non-critical UI,Eagerly loading all components at startup,"@defer (on viewport) { } @placeholder { }"," loaded at startup",High,https://angular.dev/guide/defer 30,Performance,Use NgOptimizedImage,Enforces image best practices: lazy loading LCP hints and proper sizing,NgOptimizedImage for all img tags,Plain img tags for CMS or user content,"","",High,https://angular.dev/guide/image-optimization 31,Performance,Tree-shake unused Angular features,Import only what you use from Angular packages,Import specific Angular modules needed,Import BrowserAnimationsModule when not using animations,"import { NgOptimizedImage } from '@angular/common'","import { CommonModule } from '@angular/common' // entire module",Medium,https://angular.dev/tools/cli/build 32,Performance,Avoid subscribe in components,Subscriptions leak and cause bugs; prefer async pipe or toSignal,toSignal() or async pipe instead of manual subscribe,Manual subscribe without unsubscribe in ngOnDestroy,"readonly data = toSignal(this.service.data$)","this.service.data$.subscribe(d => this.data = d)",High,https://angular.dev/guide/rxjs-interop 33,Performance,Use SSR with Angular Universal,Pre-render pages for faster LCP and better SEO,SSR or SSG for public-facing routes,Pure CSR for SEO-critical pages,"ng add @angular/ssr","// no SSR, client renders empty shell",Medium,https://angular.dev/guide/ssr 34,Performance,Minimize bundle with standalone APIs,Standalone components + provideRouter() eliminate dead NgModule code,provideRouter() and provideHttpClient() in app.config,Root AppModule with all imports,provideRouter(routes) in app.config.ts,"@NgModule({ imports: [RouterModule.forRoot(routes)] })",Medium,https://angular.dev/guide/routing/standalone 35,Testing,Use TestBed for component tests,TestBed sets up Angular DI for realistic component testing,TestBed.configureTestingModule for component tests,Instantiate components with new keyword,"TestBed.configureTestingModule({ imports: [MyComponent] })","const comp = new MyComponent()",High,https://angular.dev/guide/testing/components-basics 36,Testing,Use Angular CDK component harnesses,Harnesses provide a stable testing API that survives template refactors,MatButtonHarness and custom HarnessLoader,Direct native element queries that break on template changes,"const btn = await loader.getHarness(MatButtonHarness)","fixture.debugElement.query(By.css('button'))",Medium,https://material.angular.io/cdk/test-harnesses/overview 37,Testing,Use Spectator for less boilerplate,Spectator wraps TestBed with a cleaner API reducing test setup noise,Spectator for unit tests,Raw TestBed for every test,"const spectator = createComponentFactory(MyComponent)","TestBed.configureTestingModule({ declarations: [MyComponent] providers: [...] })",Low,https://github.com/ngneat/spectator 38,Testing,Mock services with jasmine.createSpyObj,Isolate unit tests by providing mock implementations of dependencies,SpyObj or jest.fn() mocks for services,Real HTTP calls in unit tests,"const spy = jasmine.createSpyObj('UserService' ['getUser']); spy.getUser.and.returnValue(of(user))","providers: [UserService] // real service in unit test",High,https://angular.dev/guide/testing/services 39,Testing,Write integration tests for routes,Test full route navigation including guards and resolvers,RouterTestingHarness for route integration tests,Mock all routing behavior in unit tests,"const harness = await RouterTestingHarness.create(); await harness.navigateByUrl('/home')","// manually calling route guard methods",Medium,https://angular.dev/api/router/testing/RouterTestingHarness 40,Testing,Test signal-based components,Signals update synchronously; no async flush needed in most cases,Read signal value directly in test assertions,TestBed.tick() or fakeAsync for signal reads,"component.count.set(5); expect(component.double()).toBe(10)","fakeAsync(() => { component.count.set(5); tick(); expect(component.double()).toBe(10) })",Medium,https://angular.dev/guide/testing 41,Styling,Use ViewEncapsulation.Emulated,Default emulation scopes styles to component preventing global leaks,Emulated or None for intentional global styles,ViewEncapsulation.None for component-specific styles,ViewEncapsulation.Emulated (default),ViewEncapsulation.None on feature components,Medium,https://angular.dev/guide/components/styling#style-scoping 42,Styling,Use :host selector,Style the component's host element using :host pseudo-class,":host for host element styles",Adding wrapper div just for styling,":host { display: block; padding: 1rem }","
    ...
    + .wrapper { padding: 1rem }",Medium,https://angular.dev/guide/components/styling#host-element 43,Styling,Use CSS custom properties for theming,CSS variables work across component boundaries and enable dynamic theming,CSS custom properties for colors and spacing,Hardcoded hex values in component styles,":root { --primary: #6200ee } button { background: var(--primary) }","button { background: #6200ee }",Medium,https://angular.dev/guide/components/styling 44,Styling,Integrate Tailwind with Angular,Tailwind utilities work alongside Angular's ViewEncapsulation via global stylesheet,Add Tailwind in styles.css and use utility classes in templates,Custom CSS for layout that Tailwind already handles,"
    ","
    /* .my-custom-flex { display: flex } */",Low,https://tailwindcss.com/docs/guides/angular 45,Styling,Use Angular Material theming tokens,Material 3 uses design tokens for systematic theming,M3 token-based theming for Angular Material,Overriding Angular Material CSS with deep selectors,"@include mat.button-theme($my-theme)","::ng-deep .mat-button { background: red }",Medium,https://material.angular.io/guide/theming 46,Architecture,Use injection tokens for config,Provide configuration via InjectionToken for testability and flexibility,InjectionToken for environment-specific values,Importing environment.ts directly in services,"const API_URL = new InjectionToken('apiUrl'); provide: [{ provide: API_URL useValue: env.apiUrl }]","constructor(private env: Environment) { this.url = env.apiUrl }",Medium,https://angular.dev/guide/di/dependency-injection-providers#using-an-injectiontoken-object 47,Architecture,Use HTTP interceptors,Intercept requests for auth headers error handling and logging,Functional interceptors with withInterceptors(),Service-level header management in every request,"withInterceptors([authInterceptor errorInterceptor])","httpClient.get(url { headers: { Authorization: token } }) in every call",High,https://angular.dev/guide/http/interceptors 48,Architecture,Organize by feature not type,Feature-based folder structure scales better than type-based,Feature folders with collocated component service and routes,Flat folders: all-components/ all-services/,"src/features/checkout/checkout.component.ts checkout.service.ts checkout.routes.ts","src/components/checkout.component.ts src/services/checkout.service.ts",Medium,https://angular.dev/style-guide#folders-by-feature-structure 49,Architecture,Use environment configurations,Separate environment values for dev staging and prod via Angular build configs,angular.json fileReplacements for env configs,Hardcoded API URLs or feature flags in source,"fileReplacements: [{ replace: environment.ts with: environment.prod.ts }]","const API = 'https://api.example.com' // hardcoded in service",High,https://angular.dev/tools/cli/environments 50,Architecture,Prefer inject() over constructor DI,inject() function is composable and works in more contexts than constructor injection,inject() for dependency injection,Constructor parameters for new code,"readonly http = inject(HttpClient); readonly router = inject(Router)","constructor(private http: HttpClient private router: Router) {}",Medium,https://angular.dev/api/core/inject