36 practice questions with answers for MEAN Stack interviews in Chandigarh.
MEAN Stack jobs in Chandigarh
Chandigarh, Mohali and Panchkula form the Tricity IT cluster, with IT-services firms, SaaS companies and start-ups in Mohali's IT City and Chandigarh's IT Park. Interviews usually check strong fundamentals and practical tool skills.
Below are 36 questions that match the mix of service, product and domain employers hiring mean stack developers in Chandigarh.
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01
Explain optional chaining and nullish coalescing with examples.
Optional chaining (?.) stops evaluation and returns undefined if the value before it is null or undefined, so user?.address?.city never throws. Nullish coalescing (??) provides a fallback only for null or undefined, unlike || which also replaces 0, empty string and false. So settings.pageSize ?? 10 keeps a real value of 0. Both work in TypeScript and in Angular templates.
02
How does lazy loading work with the Angular router?
Lazy loading defers downloading a feature's code until the user navigates to it. Use loadComponent: () => import('./admin/admin.component').then(m => m.AdminComponent) for a single component, or loadChildren to load a file of child routes. The CLI builds a separate chunk for each lazy route. You can add preloading strategies like withPreloading(PreloadAllModules) to fetch lazy chunks in the background after startup.
03
What is the difference between signal, computed and effect?
signal() creates writable state. computed() derives a read-only value from other signals, is lazily evaluated and memoised, and recalculates only when its dependencies change, for example a cart total from cart items. effect() runs side effects whenever signals it reads change, such as logging or syncing to local storage. Use computed for derived data and keep effects for non-UI side effects, not for setting other state.
04
How do you set up an Express project with TypeScript?
Install express and types with npm i express and npm i -D typescript @types/express @types/node. Create a tsconfig with strict mode and a module setting like NodeNext, write code in src and compile to dist with tsc. For development, run TypeScript directly with tsx watch, and use node dist/server.js in production. Type request bodies, params and responses with Request and Response generics or validated schemas.
05
How do you approach learning a new framework version or language feature on the job?
Situation: our team decided to adopt Angular signals in new features. Task: I had to use them in a sprint while still delivering. Action: I read the official guide, built a small sample, compared it with our RxJS patterns, then implemented one component and asked a senior to review. I shared a short note with examples for the team. Result: my component became the reference pattern for later features.
06
Tell me about a time you improved test coverage or quality in a project.
Situation: our MEAN project had almost no tests and every release broke something. Task: I volunteered to improve this. Action: I set up Supertest with an in-memory MongoDB for critical APIs, added component tests for checkout, wrote a short testing guide and made tests required in CI. I started with the five most bug-prone areas. Result: production bugs per release dropped sharply within three months.
07
What are Angular's lifecycle hooks and when is each typically used?
ngOnChanges runs when input values change. ngOnInit runs once after the first inputs are set, used for initial data loading. ngDoCheck allows custom change detection. ngAfterContentInit and ngAfterViewInit run after projected content and the view are ready, used for DOM access. ngOnDestroy runs before removal, used for cleanup. With signals, effect, computed and DestroyRef often replace several of these hooks.
08
Write an aggregation that finds the top five customers by total spend with their names.
Utility types transform existing types instead of duplicating them. Partial<User> makes all fields optional, useful for update payloads. Pick<User, 'id' | 'name'> selects fields, and Omit<User, 'password'> removes them, handy for safe API responses. Record<string, number> describes an object map with typed keys and values. Readonly<T> and Required<T> are also common, and they keep frontend and backend models consistent.
10
An Express endpoint generates a large PDF report and the whole API slows down while it runs. How do you fix it?
PDF generation is CPU-heavy and blocks the event loop. Move it to a background job: the endpoint creates a job in a queue such as BullMQ with Redis and immediately returns 202 Accepted with a job id. A separate worker generates the PDF, uploads it to storage and updates the job status. Angular polls the status or receives a websocket notification, then downloads the file.
11
Define a typed Mongoose model in TypeScript with an instance method.
Change detection checks component bindings and updates the DOM when data changes. Traditionally Zone.js patched async APIs and triggered a check of the whole tree after events, timers and HTTP calls. With ChangeDetectionStrategy.OnPush, a component is checked only when an input reference changes, an event fires inside it, an async pipe emits or a signal it reads changes. OnPush with immutable data greatly reduces work.
13
After deploying the Angular app behind a load balancer, navigating directly to /orders/42 gives a 404. What is wrong?
The Angular router handles that path in the browser, but the web server looks for a real file at /orders/42 and finds none. Configure the server to return index.html for unknown routes: try_files $uri $uri/ /index.html in Nginx, a rewrite rule in IIS or static hosting, or a catch-all route in Express that serves the built index.html after API routes. Alternatively use server-side rendering.
14
How do toSignal and toObservable bridge RxJS and signals?
toSignal(observable$) subscribes to an Observable and exposes its latest value as a signal, unsubscribing automatically when the injection context is destroyed; you can supply an initialValue or requireSync. toObservable(signal) creates an Observable that emits whenever the signal changes, letting you apply RxJS operators like debounceTime and switchMap. Together they let you keep simple state in signals while using RxJS for async logic.
15
Write a functional HTTP interceptor that adds a JWT and handles 401 errors.
A Subject is both an Observable and an observer, multicasting values to subscribers but giving late subscribers nothing from the past. BehaviorSubject needs an initial value and gives the latest value to new subscribers, popular for state like the current user. ReplaySubject replays a set number of past values. AsyncSubject emits only the final value on completion. In new code, signals often replace BehaviorSubject for state.
17
An npm audit shows several high-severity vulnerabilities in the Express project. How do you handle it?
Read each advisory to see whether the vulnerable code path is actually used in production or only in dev tooling. Run npm audit fix for safe updates, upgrade direct dependencies that pull vulnerable transitive packages, and use overrides in package.json if a fix is not yet released upstream. Test thoroughly after upgrading, enable Dependabot or Renovate for continuous updates and track any accepted risks.
18
Users double-click the Pay button and two payment requests are sent. How would you prevent it on the frontend?
Disable the button while the request is pending, using an isSubmitting signal. In RxJS, model clicks as a stream and use exhaustMap, which ignores new clicks until the current payment request completes. Show a loading state and handle errors so the button re-enables. The backend must still use idempotency keys, because frontend protection alone cannot stop network retries or duplicate tabs.
19
Explain the any, unknown and never types in TypeScript.
any switches off type checking, so any operation is allowed and errors move to runtime. unknown also accepts any value but forces you to narrow it with typeof, instanceof or a type guard before using it, making it the safe choice for parsed JSON or caught errors. never represents values that never occur, such as a function that always throws, and is used in exhaustive switch checks.
20
Write a type-ahead search using a reactive FormControl and RxJS operators.
Middleware is a function with access to req, res and next that runs in order for matching requests. Kinds include application-level middleware registered with app.use, router-level middleware on an express.Router, built-in middleware like express.json and express.static, third-party middleware such as cors, helmet and morgan, and error-handling middleware with four arguments. Middleware can end the response or pass control with next().
22
What is the difference between valueChanges and statusChanges, and what does updateOn do?
valueChanges is an Observable that emits the new value whenever a control or group changes, useful for dependent fields or type-ahead search. statusChanges emits when validation status changes between VALID, INVALID, PENDING and DISABLED. The updateOn option controls when value and validation update: change by default, blur to validate when the field loses focus, or submit to validate only on form submission.
23
What is the inject() function and how does it compare to constructor injection?
inject() retrieves a dependency inside an injection context, such as a field initialiser, constructor, factory or functional guard. It removes long constructor parameter lists, works in plain functions like functional guards, interceptors and resolvers, and makes inheritance simpler because subclasses do not need to pass dependencies to super. Constructor injection still works, but modern Angular code and CLI templates favour inject().
24
What is the difference between template-driven and reactive forms in Angular?
Template-driven forms build the form model from directives in the template, mainly ngModel, and suit small, simple forms. Reactive forms define the model explicitly in the component with FormControl, FormGroup and FormArray, giving synchronous access, strong typing, easier dynamic fields, observable valueChanges and simpler unit testing. Most enterprise Angular applications use reactive forms for complex or validated forms.
25
Write a cart service using signals with computed totals.
HttpClient is Angular's service for making HTTP requests. It returns Observables, automatically parses JSON, supports typed responses with generics, interceptors, progress events and request cancellation by unsubscribing. In a standalone app you register it with provideHttpClient() in app.config.ts, optionally with withInterceptors([...]) and withFetch() to use the Fetch API, which is recommended for server-side rendering.
27
A form must show fields based on earlier answers, such as company name only when employment type is salaried. How would you build it?
Subscribe to the employment type control's valueChanges, or use a signal, and enable or disable the dependent controls accordingly; disabled controls are excluded from value and validation. Show the fields in the template with @if. For forms driven by configuration, build controls dynamically from a JSON schema into a FormGroup. Remember to clear stale values when a field is hidden.
28
Implement a type-ahead search box that calls the API only after the user pauses typing and ignores outdated results. Which RxJS approach would you use?
Take the input stream from a FormControl's valueChanges or toObservable of a signal, then pipe debounceTime(300) to wait for a pause, map to trimmed text, filter out terms shorter than two characters, distinctUntilChanged to skip repeats, and switchMap to call the API, which cancels any in-flight request when a new term arrives. Add catchError inside switchMap so one failed request does not kill the stream.
29
How does Angular protect against cross-site scripting?
Angular treats all values as untrusted by default and sanitises them before inserting into the DOM: interpolation escapes HTML, and binding to innerHTML, styles or URLs is sanitised to strip dangerous content. Bypass methods in DomSanitizer, like bypassSecurityTrustHtml, should be used only for trusted content. Avoid direct DOM manipulation through ElementRef with user data, and add a Content Security Policy for defence in depth.
30
How do you handle disagreements with a UI designer about how a form should behave?
Situation: a designer wanted validation errors only after submit, but users were missing errors on long forms. Task: reach an agreement quickly. Action: I shared quick screen recordings comparing both approaches and pointed to accessibility guidelines, then proposed validation on blur with a summary at the top on submit. Result: the designer agreed, we tested it with users and the pattern became part of our design system.
31
Write an Nginx server block that serves Angular and proxies /api to Node.
Situation: users sometimes saw another customer's details after quickly switching between records. Task: find the cause in a busy sprint. Action: I reproduced it with network throttling and found nested subscribes, where slow responses for an earlier id arrived last. I replaced them with switchMap so stale requests were cancelled, and added a test with delayed responses. Result: the bug disappeared and we added a review rule against nested subscribes.
33
An order form lets users add any number of items with product, quantity and price. How do you build it?
Use a FormArray of FormGroups, each with product, quantity and price controls and validators like min(1). Provide addItem and removeItem methods that push or removeAt on the array, and render rows with @for over items.controls. Calculate the total from valueChanges or a computed signal. On submit, send getRawValue() typed as the order DTO, and disable the submit button while invalid or pending.
34
An API sometimes returns null for a nested field and the Angular app crashes with cannot read properties of undefined. How do you fix it properly?
Model the API response accurately in TypeScript, marking the field as optional or nullable, and keep strictNullChecks on so the compiler forces you to handle it. Use optional chaining in code and templates, provide defaults with ??, and show a fallback in the UI with @if. Also agree with the backend team on the contract, and validate responses at the boundary if the data is untrusted.
Define a TypeScript interface for the document, then create a Schema typed with that interface and a model with model<IUser>('User', userSchema). Mongoose infers types for queries, so findById returns a typed document. For lean queries, results are plain typed objects. Schema options like timestamps add createdAt and updatedAt, and you can type instance methods, statics and virtuals through additional generic parameters.
36
You are building an e-commerce product catalogue where each category has different attributes, such as size for clothes and RAM for laptops. How would you model it in MongoDB?
Store common fields like name, price, category and stock at the top level, and keep variable specifications in an attributes array of { key, value } pairs, the attribute pattern. Create a compound index on attributes.key and attributes.value so filters work on any attribute. This avoids dozens of sparse fields and lets new categories be added without schema changes, while Mongoose validates the common fields.
Few big employers listed in Chandigarh?
Many Chandigarh candidates also apply to teams in Gurgaon and to remote or hybrid roles. Practise the Gurgaon set as well.
Which companies hire MEAN Stack professionals in Chandigarh?
Companies with large offices in Chandigarh include many IT services and product firms. Use their company pages below to practise employer-specific sets.
Are MEAN Stack interviews in Chandigarh different from other cities?
The questions depend more on the company than the city. Chandigarh's mix of employers decides the style: Interviews usually check strong fundamentals and practical tool skills
How do I find MEAN Stack jobs in Chandigarh?
Shortlist companies with Chandigarh offices, keep your CV focused on MEAN Stack projects, apply on company career pages and job portals with the Chandigarh filter, and practise the questions on this page before each interview.