Interview Q&A

Short answer: Follow me on LinkedIn: Bootstrap is a popular front-end framework for building responsive, mobile-first web pages using HTML, CSS, and JavaScript components.

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: They are part of the browser’s rendering process when the DOM or styles change.

Explain a bit more

Reflow (Layout): Happens when the structure or geometry of the page changes (like changing size, position, or adding elements). → Expensive operation since it recalculates layout. Follow me on LinkedIn: Repaint: Happens when visual appearance (like color or background) changes without affecting layout. Example: div.style.width = "200px"; /* triggers reflow + repaint */

Example code

div.style.background = "red"; /* triggers repaint only */ Key Takeaway: Minimize layout changes; batch DOM updates to improve performance.

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: block elements take full width and start on a new line. inline-block behaves like inline (stays in the same line) but allows setting width, height, margin, and padding.

Example code

.block { display: block; width: 100px; } .inline-block { display: inline-block; width: 100px; } Key Takeaway: inline-block combines the flow of inline with the flexibility of block. Follow me on LinkedIn:

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: JavaScript is a high-level, interpreted programming language primarily used for web development to make webpages interactive. Example: alert('Hello World!');

Example code

JavaScript is a high-level, interpreted programming language primarily used for web development to make webpages interactive. Example: alert('Hello World!');

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: The event loop manages asynchronous operations in JavaScript. It continuously checks the call stack and callback queue — executing queued tasks once the stack is empty.

Example code

console.log("A"); setTimeout(() => console.log("B"), 0); console.log("C"); // Output: A, C, B Even though setTimeout is 0ms, it runs after the main thread finishes due to the event loop.

Real-world example (ShopNest)

The checkout button uses async/await to call /api/orders, shows a spinner, and catches network errors with a toast.

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1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Flexbox (Flexible Box Layout) is a one-dimensional layout system for aligning items horizontally or vertically.

Example code

.container { display: flex; justify-content: center; align-items: center; } Why use it: Centers elements easily. Handles spacing and alignment dynamically. Makes layouts responsive. Key Takeaway: Flexbox simplifies alignment and space distribution in one direction.

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: The <!DOCTYPE html> declaration tells the browser which version of HTML the page uses. In modern websites, it triggers HTML5 standards mode, ensuring consistent rendering across browsers. Example: <!DOCTYPE html> <html> ... </html> Key Takeaway: Always include <!DOCTYPE html> at the top of every HTML file.

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: lignment Easier for single direction Easier for full layout structure /* Flexbox */ display: flex; /* Grid */ Follow me on LinkedIn: display: grid; grid-template-columns: repeat(3, 1fr); Key Takeaway: Use Flexbox for alignment; Grid for complete layouts. lignment Easier for single direction Easier for full layout structure

Example code

/* Flexbox */ display: flex; /* Grid */ Follow me on LinkedIn: display: grid; grid-template-columns: repeat(3, 1fr); Key Takeaway: Use Flexbox for alignment; Grid for complete layouts. lignment Easier for single direction Easier for full layout structure Example: /* Flexbox */ display: flex; /* Grid */ Follow me on LinkedIn: display: grid; grid-template-columns: repeat(3, 1fr); Key Takeaway: Use Flexbox for alignment; Grid for complete layouts.

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Feature Bootstrap 4 Bootstrap 5 jQuery Required Removed Grid 5 breakpoints 6 (added xxl) Forms Legacy Redesigned Icons None Separate Bootstrap Icons Utility API Limited Expanded and customizable

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Garbage collection automatically frees memory that’s no longer referenced. The V8 engine uses the mark-and-sweep algorithm: “Mark” reachable objects from the root. “Sweep” and delete unreachable ones. Example: let user = { name: "John" };

Example code

user = null; // eligible for garbage collection

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Feature Flexbox Grid Layout One-dimensional (row or column) Two-dimensional (rows and columns) Use Case Aligning items in a line Building full-page layouts Alignment Easier for single direction Easier for full layout structure

Example code

/* Flexbox */ display: flex; /* Grid */ Follow me on LinkedIn: display: grid; grid-template-columns: repeat(3, 1fr); Key Takeaway: Use Flexbox for alignment; Grid for complete layouts.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Example: <user-card></user-card> <template id="user-template"> <p>Hello, <span id="name"></span></p> </template> <script> class UserCard extends HTMLElement { connectedCallback() { const tmpl = document.getElementById("user-template");

Example code

const content = tmpl.content.cloneNode(true);
content.querySelector("#name").textContent = "Sandeep"; this.appendChild(content); }
} customElements.define("user-card", UserCard); </script> Key Takeaway: Web Components = reusable, encapsulated building blocks for modern web apps.

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: The Shadow DOM is a web component feature that encapsulates a section of the DOM — meaning styles and markup inside it don’t leak out or get affected by the rest of the page. Example: <custom-card></custom-card> <script> class CustomCard extends HTMLElement { constructor() { super(); const shadow = this.attachShadow({ mode: 'open' });

Example code

shadow.innerHTML = `<style>p { color: blue; }</style><p>Hello Shadow!</p>`; }
} customElements.define('custom-card', CustomCard); </script> Key Takeaway: Shadow DOM = style and structure isolation for reusable, predictable components.

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: The <canvas> element is used to draw graphics, animations, charts, or games using JavaScript. Example: <canvas id="myCanvas" width="200" height="100"></canvas> <script> const canvas = document.getElementById("myCanvas"); ctx.fillStyle = "blue"; ctx.fillRect(10, 10, 180, 80); </script> Follow me on LinkedIn: Key Takeaway: <canvas> gives you a pixel-based drawing area inside HTML — perfect for dynamic graphics.

Example code

const ctx = canvas.getContext("2d");

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: pply () Same as call(), but takes array Array ✅ Yes bind( Returns a new function with fixed this Comma-separat ed ❌ No function greet(greeting) { console.log(`${greeting}, ${this.name}`); } const user = { name: "John" }; greet.call(user, "Hi"); greet.apply(user, ["Hello"]); const bound = greet.bind(user, "Hey"); bound(); … pply () Same as call(),… but takes array Array ✅ Yes bind( Returns a new function with fixed…

Example code

function greet(greeting) { console.log(`${greeting}, ${this.name}`); } const user = { name: "John" }; greet.call(user, "Hi"); greet.apply(user, ["Hello"]); const bound = greet.bind(user, "Hey"); bound(); pply () Same as call(), but takes array Array ✅ Yes bind( Returns a new function with fixed this Comma-separat ed ❌ No Example: function greet(greeting) { console.log(`${greeting}, ${this.name}`); } const user = { name: "John" }; greet.call(user, "Hi"); greet.apply(user, ["Hello"]); const bound = greet.bind(user, "Hey"); bound(); … pply () Same as call(), but takes array Array ✅ Yes bind( Returns a new function with fixed this Comma-separat ed ❌ No Example: function greet(greeting) { console.log(`${greeting}, ${this.name}`); } const user = { name: "John" }; greet.call(user, "Hi"); greet.apply(user, ["Hello"]); const bound = greet.bind(user, "Hey"); bound();

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: A container wraps page content and provides horizontal padding. <div class="container">Content</div> <div class="container-fluid">Full width</div>

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: A service worker is a background script that runs independently of the web page. It enables offline caching, push notifications, and background sync.

Example code

navigator.serviceWorker.register('/sw.js'); ✅ Used in Progressive Web Apps (PWAs).

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Metho Purpose Arguments Invokes Immediately? call( Call a function with a specific this Comma-separat ed ✅ Yes apply () Same as call(), but takes array Array ✅ Yes bind( Returns a new function with fixed this Comma-separat ed ❌ No Example: function greet(greeting) { console.log(`${greeting}, ${this.name}`); }

Example code

const user = { name: "John" }; greet.call(user, "Hi"); greet.apply(user, ["Hello"]); const bound = greet.bind(user, "Hey"); bound();

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Type Scope Example Priority Inline Single element style="color:re d;" Highest Internal One page <style> inside <head> Medium External Multiple pages Linked .css file Lowest Key Takeaway: Use external CSS for maintainable, large-scale projects. Follow me on LinkedIn:

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Both store data in the browser, but they differ in duration and scope. Feature localStorage sessionStorage Lifetime Until manually cleared Until the tab is closed Scope Shared across tabs Specific to one tab Capacity ~5–10MB ~5MB

Example code

localStorage.setItem("username", "Sandeep"); sessionStorage.setItem("theme", "dark"); Key Takeaway: Use localStorage for long-term data; sessionStorage for temporary, tab-specific data.

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: <div> is a block-level element (creates a full-width container). <span> is an inline element (used for styling small text portions).

Example code

<div>Block Section</div> <p>This is a <span style="color: red;">red word</span> in a sentence.</p> Key Takeaway: Use <div> for layout; <span> for inline styling.

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: In JavaScript, every object can inherit properties from another object called its prototype. This enables object reusability. Example: const animal = { eats: true };

Example code

const dog = Object.create(animal); Follow me on LinkedIn: dog.barks = true; console.log(dog.eats); // true (inherited)

Real-world example (ShopNest)

Prefer arrow functions for React/event callbacks in ShopNest so this is not accidentally rebound.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Follow me on LinkedIn: Aspect @import <link> Loaded Inside CSS Inside HTML <head> Performance Slower (sequential) Faster (parallel) Media Queries Can include Can include Recommended ❌ Avoid ✅ Preferred Key Takeaway: Use <link> — it loads faster and supports preloading and caching better.

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Every HTML element is a box made of:

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.

Short answer: Lazy loading defers loading of non-critical images or iframes until they are visible in the viewport — improving page speed.

Example code

<img src="photo.jpg" loading="lazy" alt="Nature view"> Key Takeaway: loading="lazy" helps reduce initial load time and saves bandwidth.

Real-world example (ShopNest)

ShopNest’s browser cart uses modern JavaScript: fetch APIs with async/await, modules, and clear error handling.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.