Easy MEAN Stack Interview Questions

A generic wrapper avoids repeating pagination fields. export interface Paginated<T> { items: T[]; page: number; totalPages: number; } export interface Product { _id: string; name: string; price: number; tags?: string[]; } getProducts(page = 1): Observable<Paginated<Product>> { return this.http.get<Paginated<Product>>('/api/products', { params: { page } }); }

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 }]); }

Pipes are standalone by default. import { Pipe, PipeTransform } from '@angular/core'; @Pipe({ name: 'truncate' }) export class TruncatePipe implements PipeTransform { transform(value: string | null, limit = 50): string { if (!value) return ''; return value.length > limit ? value.slice(0, limit).trimEnd() + '...' : value; } } // add TruncatePipe to the component's imports, then: // {{ product.description | truncate:80 }} Because it is pure, it reruns only when the input string or limit changes.

Common commands: ng new shop-app --style=scss ng serve --open ng generate component features/product-list ng generate service core/auth ng generate guard core/auth --functional ng generate pipe shared/truncate ng build --configuration production ng test ng update @angular/core @angular/cli ng update applies official migrations automatically, which makes version upgrades much easier.

Signals keep simple state readable. import { Component, signal, computed, effect } from '@angular/core'; @Component({ selector: 'app-counter', template: ` <p>Count: {{ count() }} (double: {{ double() }})</p> <button (click)='increment()'>+</button> <button (click)='count.set(0)'>Reset</button> ` }) export class CounterComponent { count = signal(0); double = computed(() => this.count() * 2); constructor() { effect(() => console.log('count changed to', this.count())); } increment() { this.count.update((c) => c + 1); } }

Typed controls and disabled submit while invalid. export class LoginComponent { private fb = inject(NonNullableFormBuilder); form = this.fb.group({ email: ['', [Validators.required, Validators.email]], password: ['', [Validators.required, Validators.minLength(8)]] }); submit() { if (this.form.invalid) return this.form.markAllAsTouched(); this.auth.login(this.form.getRawValue()).subscribe(); } } // template // <form [formGroup]='form' (ngSubmit)='submit()'> // <input formControlName='email'> // @if (form.controls.email.hasError('email')) { <small>Invalid email</small> } // <button [disabled]='form.invalid'>Login</button> // </form>

Generics type params and response bodies. import { Router, Request, Response } from 'express'; import { Product } from '../models/product.model'; const router = Router(); router.get('/:id', async (req: Request<{ id: string }>, res: Response) => { const product = await Product.findById(req.params.id).lean(); if (!product) { return res.status(404).json({ message: 'Product not found' }); } res.json(product); }); export default router; // app.use('/api/products', router);

proxy.conf.json in the Angular project: { "/api": { "target": "http://localhost:3000", "secure": false, "changeOrigin": true, "logLevel": "debug" } } angular.json, under serve options: "proxyConfig": "proxy.conf.json" Then call relative URLs in services, such as this.http.get('/api/products'), and run ng serve. The browser talks only to the dev server, so no CORS setup is needed locally.

Chain query helpers and run count in parallel. const filter = { category: req.query.category, price: { $gte: Number(req.query.min) || 0 }, isActive: true }; const [items, total] = await Promise.all([ Product.find(filter) .select('name price images rating') .sort({ rating: -1, _id: 1 }) .skip((page - 1) * limit) .limit(limit) .lean(), Product.countDocuments(filter) ]); Adding _id to the sort keeps the order stable between pages.

Extend the request type with the user. import jwt from 'jsonwebtoken'; import { Request, Response, NextFunction } from 'express'; export interface AuthRequest extends Request { user?: { id: string; role: string } } export function auth(req: AuthRequest, res: Response, next: NextFunction) { const token = req.headers.authorization?.split(' ')[1]; if (!token) return res.status(401).json({ message: 'Unauthorized' }); try { req.user = jwt.verify(token, process.env.JWT_SECRET!) as AuthRequest['user']; next(); } catch { res.status(401).json({ message: 'Token invalid or expired' }); } }