MEAN Stack Interview Questions in Lucknow

app.routes.ts: import { Routes } from '@angular/router'; export const routes: Routes = [ { path: '', loadComponent: () => import('./home/home.component').then(m => m.HomeComponent) }, { path: 'products', loadChildren: () => import('./products/product.routes').then(m => m.PRODUCT_ROUTES) }, { path: 'login', loadComponent: () => import('./auth/login.component').then(m => m.LoginComponent) }, { path: '**', loadComponent: () => import('./not-found.component').then(m => m.NotFoundComponent) } ]; // app.config.ts providers: [provideRouter(routes, withComponentInputBinding())]

Tokens carry non-class values. import { InjectionToken, inject, Injectable } from '@angular/core'; export interface AppConfig { apiUrl: string; pageSize: number } export const APP_CONFIG = new InjectionToken<AppConfig>('APP_CONFIG'); // app.config.ts providers: [{ provide: APP_CONFIG, useValue: { apiUrl: environment.apiUrl, pageSize: 20 } }] @Injectable({ providedIn: 'root' }) export class OrderService { private config = inject(APP_CONFIG); private http = inject(HttpClient); list() { return this.http.get(`${this.config.apiUrl}/orders`, { params: { limit: this.config.pageSize } }); } }

A typical strict configuration: { "compilerOptions": { "target": "ES2022", "module": "NodeNext", "moduleResolution": "NodeNext", "outDir": "dist", "rootDir": "src", "strict": true, "noUncheckedIndexedAccess": true, "esModuleInterop": true, "skipLibCheck": true, "sourceMap": true }, "include": ["src"] } noUncheckedIndexedAccess adds undefined to indexed lookups, catching missing keys.

Useful diagnostic commands: db.orders.getIndexes() db.orders.find({ status: 'pending', city: 'Pune' }) .sort({ createdAt: -1 }) .explain('executionStats') db.setProfilingLevel(1, { slowms: 100 }) db.system.profile.find().sort({ ts: -1 }).limit(5) db.orders.createIndex({ status: 1, city: 1, createdAt: -1 }) Compare totalDocsExamined with nReturned before and after creating the index.

Expose read-only state and mutation methods. @Injectable({ providedIn: 'root' }) export class CartService { private items = signal<CartItem[]>([]); readonly cart = this.items.asReadonly(); readonly count = computed(() => this.items().reduce((n, i) => n + i.qty, 0)); readonly total = computed(() => this.items().reduce((s, i) => s + i.qty * i.price, 0)); add(product: Product) { this.items.update((list) => { const found = list.find((i) => i.id === product.id); return found ? list.map((i) => (i.id === product.id ? { ...i, qty: i.qty + 1 } : i)) : [...list, { ...product, qty: 1 }]; }); } remove(id: string) { this.items.update((l) => l.filter((i) => i.id !== id)); } }

Group, sort, limit, then join. db.orders.aggregate([ { $match: { status: 'paid' } }, { $group: { _id: '$customerId', spend: { $sum: '$total' }, orders: { $sum: 1 } } }, { $sort: { spend: -1 } }, { $limit: 5 }, { $lookup: { from: 'users', localField: '_id', foreignField: '_id', as: 'customer' } }, { $unwind: '$customer' }, { $project: { _id: 0, name: '$customer.name', spend: 1, orders: 1 } } ]) Joining after $limit means only five lookups run.

Build in Node, ship only static files. FROM node:22-alpine AS build WORKDIR /app COPY package*.json ./ RUN npm ci COPY . . RUN npx ng build --configuration production FROM nginx:alpine COPY nginx.conf /etc/nginx/conf.d/default.conf COPY --from=build /app/dist/shop/browser /usr/share/nginx/html EXPOSE 80 The final image contains no Node.js or source code. nginx.conf should include try_files $uri /index.html for Angular routes.

Capture and flush the request. describe('ProductService', () => { let service: ProductService; let httpMock: HttpTestingController; beforeEach(() => { TestBed.configureTestingModule({ providers: [provideHttpClient(), provideHttpClientTesting()] }); service = TestBed.inject(ProductService); httpMock = TestBed.inject(HttpTestingController); }); it('fetches products', () => { service.getAll().subscribe((p) => expect(p.length).toBe(1)); const req = httpMock.expectOne('/api/products'); expect(req.request.method).toBe('GET'); req.flush([{ _id: '1', name: 'Pen' }]); httpMock.verify(); }); });

Signals and built-in control flow keep it concise. import { Component, signal } from '@angular/core'; import { CurrencyPipe } from '@angular/common'; @Component({ selector: 'app-product-list', imports: [CurrencyPipe], template: ` @for (p of products(); track p.id) { <div class='card'>{{ p.name }} - {{ p.price | currency:'INR' }}</div> } @empty { <p>No products found</p> } ` }) export class ProductListComponent { products = signal([{ id: 1, name: 'Laptop', price: 55000 }]); }

A ValidatorFn returns null or an error map. import { AbstractControl, ValidationErrors, ValidatorFn } from '@angular/forms'; export function strongPassword(): ValidatorFn { return (control: AbstractControl): ValidationErrors | null => { const value = control.value as string; if (!value) return null; const ok = /[A-Z]/.test(value) && /\d/.test(value); return ok ? null : { weakPassword: true }; }; } // password: ['', [Validators.required, strongPassword()]] // @if (form.controls.password.hasError('weakPassword')) { ... }