Angular
123 bites tagged Angular: interview questions with model answers, and 60-second explainers.
Test yourself: Top 30 Angular interview questions →Multiple choice, with the correct answer and why it is correct on every question. Free, no sign-in.Angular is decoupling its compiler from TypeScript APIs
Angular says it is building an Angular-specific compiler so the framework can benefit from TypeScript 7’s native tooling without depending on its compiler APIs.
Angular v22 stabilizes Signal Forms, Aria, Asynchronous Reactivity APIs
Angular v22 promotes Signal Forms, Angular Aria, and Asynchronous Reactivity APIs from developer preview to production-ready status, giving teams stable primitives for reactive forms, accessibility, and async signals without experimental guardrails.
Angular v21 ships while AI models write outdated code
Angular v21 ships while standard AI models still write outdated code. Zoneless architecture and Signals now dominate performance roadmaps. Audit AI PRs for legacy patterns and verify zoneless readiness before Q3.
Angular 21.1 ships with Signal Forms debounce patterns
Angular 21.1 ships with minor fixes. Signal Forms tutorials now show debounced async validators to cut wasted backend API calls. Migration guides for the modern Control Flow syntax are available for apps still on legacy structural directives.
Angular Universal server memory leak: causes and diagnosis
Incomplete platform destruction, global DOM polyfills, unclosed RxJS; use heap snapshots and --inspect.
What is the difference between ChangeDetectionStrategy.Default and ChangeDetectionStrategy.OnPush in Angular?
Default checks components on most async events; OnPush checks on input changes, DOM events, or async pipe emits.
How do Vue, Angular, and Svelte stores trigger component re-renders?
Tests deep knowledge of reactivity primitives. Contrast Vue's proxy subscriptions, Angular's RxJS push through async pipe or markForCheck, and Svelte's compiler-generated store invalidation. Red flag: claiming all three use virtual DOM diffing or polling.
What is Angular Ivy's 'locality' and its benefits over View Engine?
Tests Ivy's per-file compilation model. Locality compiles decorators to static properties without global knowledge, except components need their NgModule scope, speeding builds and tree-shaking.
How does ngc work in Angular AOT and what artifacts improve performance?
This tests understanding of AOT build-phase compilation and output. Cover efficient JS output, inlined templates and styles cutting AJAX requests, and removal of compiler payload roughly half of Angular. Red flag: conflating AOT and JIT or calling it bundling.
Create a custom synchronous validator for an Angular Reactive Form
Tests your grasp of the ValidatorFn contract and reactive form wiring. A strong answer: a function accepting AbstractControl returns null when valid or an error object when invalid, passed as the second FormControl argument. Red flag: returning booleans.
How do Vue, Angular, and Svelte handle deep prop mutation re-rendering?
Vue and Svelte detect nested mutations via Proxies; Angular default re-renders via Zone.js, but ngOnChanges misses it since the reference is unchanged.
How does Angular's Zone.js change detection differ from Vue and Svelte reactivity?
Tests granular reactivity architecture. Angular Zone.js monkey-patches async to scan the full component tree; Vue uses runtime Proxy tracking; Svelte compiles runes into targeted DOM bindings.
Explain server.ts and main.ts in Angular Universal
Server.ts SSRs initial HTML via Node/Express; main.ts bootstraps the browser app and hydrates the DOM. First request hits the server; later navigations are client-side only.
Compare Angular Zone.js and Vue 3 Proxy reactivity
This tests update granularity. Contrast Vue 3 Proxy tracking, targeting only affected components, with Angular Zone.js patching async APIs to trigger top-down dirty checking across tree. Vue binds deps at render; Angular compares values each cycle.
How would you diagnose and optimize slow Angular component tests?
Tests Angular test economics and runner overhead. Strong answers profile with Vitest, swap Karma for jsdom/happy-dom, mock services, and reduce TestBed recompilation via targeted imports.
How do you mock an async service call in an Angular component test?
This tests Angular unit isolation and HTTP mocking. A strong answer covers HttpTestingController setup, flushing a mock response, asserting UI changes, and notes mocking avoids flaky networks. Red flag: using real HTTP calls in unit tests.
What is Angular's TestBed and when would you use it?
Say createComponent returns a fixture with no immediate binding, so await fixture.whenStable before asserting DOM.
What is the fundamental difference between unit and component tests?
Isolation levels in frontend testing. Unit tests verify single functions or composables with mocked dependencies; component tests verify mounting, rendering, and interaction and pull in more code.
Why does an OnPush Angular child not update when its input changes?
Tests OnPush reference equality and manual change detection. Strong answers name: in-place object mutation as the root cause; ChangeDetectorRef.markForCheck or detectChanges to force updates; and Angular Signals as a modern path.
How do you lazy-load a route in Vue or Angular?
Tests route-level code splitting. Strong answers mention dynamic imports in Vue Router or Angular loadChildren and highlight a smaller initial JS bundle. Red flag: confusing this with image lazy loading or claiming it speeds up runtime navigation.
When would you provide an Angular service at the component level?
Tests Angular DI scoping beyond singletons. A strong answer picks stateful reusable widgets, explains providers create one instance per subtree, and notes cleanup on destroy. Red flag: claiming this is for performance without mentioning state isolation.
Architect reusable form validation in Vue vs Angular
Tests how you encapsulate reactive state across frameworks. Contrast Vue's useForm composable returning refs and lifecycle hooks. Contrast Angular's service exposing a FormGroup via RxJS.
Would you use a Service or a custom Pipe for currency formatting?
Choose Pipe for declarative syntax; implement PipeTransform with transform(value, ...args); use Intl.NumberFormat; register standalone.
How to create a singleton Angular auth service
Tests Angular dependency injection and singleton scope. Strong answer: use the Injectable decorator with providedIn set to root for an application-wide singleton, then inject it into components.
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