👋 Hi everyone, I recently appeared for a Front-End Developer Interview and wanted to share some really interesting questions asked across both rounds. 🎯 Round 1 – Technical (JavaScript, TypeScript & Angular) 1️⃣ Difference between == and === Ans: == checks value (performs type coercion), while === checks value + type (strict comparison). 2️⃣ How do Promises work? Explain .then() and .catch() Ans: Promise represents async completion. .then() handles success, .catch() handles errors. 3️⃣ What is Hoisting in JavaScript? Ans: JS moves declarations (not initialization) to the top of scope before execution. 4️⃣ How does Change Detection work in Angular? Ans: Angular checks component tree to detect data changes and update the DOM using zones. 5️⃣ Difference between Reactive Forms and Template-Driven Forms Ans: Reactive = code-driven, scalable, testable. Template-driven = HTML-driven, easy but less scalable. 6️⃣ How does async / await work internally? Ans: It is syntactic sugar over Promises—await pauses inside async function until Promise resolves. 7️⃣ What is Lazy Loading in Angular? Ans: Loading modules on demand to reduce initial bundle size and improve performance. 8️⃣ Difference between Observables and Subjects in RxJS Ans: Observable is unicast (each subscriber gets its own stream), Subject is multicast (same stream for all). 9️⃣ What is a Pure Pipe in Angular? Ans: A pipe that runs only when inputs change (no re-execution on every change detection cycle). 🔟 What is CORS and where do we enable it? Ans: A security feature that allows/blocks cross-domain requests. Enabled on server (API) side. 💻 Round 2 – Practical & Scenario-Based 1️⃣ Bind API response data into a table with pagination and search Ans: Fetch data → store in state → apply filter & slicing → display using *ngFor. 2️⃣ Implement form validation and dynamic error messages Ans: Use Angular Validators; show errors using formControl.errors. 3️⃣ Pass data using @Input() and @Output() Ans: @Input() → parent to child; @Output() + EventEmitter → child to parent. 4️⃣ How to optimize a slow Angular page? Ans: Use OnPush, trackBy, Lazy Loading, avoid heavy loops, unsubscribe from Observables. 5️⃣ Difference between Local Storage, Session Storage, and Cookies Ans: Local = persistent, Session = ends on tab close, Cookies = small data sent with every request. 6️⃣ Implement Debouncing for a search field Ans: Use debounceTime() in RxJS or use setTimeout pattern. 7️⃣ Subject vs BehaviorSubject Ans: BehaviorSubject stores initial value + last emitted value; Subject does not. 8️⃣ Use of trackBy in *ngFor Ans: Prevents re-rendering by uniquely identifying list items → boosts performance. #Angular #JavaScript #TypeScript #FrontendDevelopment #WebDevelopment #AngularInterview #FrontendInterview #TechCareer #CodingInterviews #RxJS #LinkedInTech #AngularDeveloper #MERN #UIDeveloper
Great shortlist! I would add there some questions about latest zoneless versions of Angular, signals, standalone components, SSR etc.
Answer to question 2 is strange? The .then() also catches errors/rejections with its second argument, as I remember. The .catch() method is called only if an error/rejection hasn't been caught by any previous thens.