JavaScript Frameworks

Table of Contents

• What Are JavaScript Frameworks?
• Why Use JavaScript Frameworks?
• Most Popular Frameworks (2025)
• Framework Comparison Table
• Library vs Framework
• Popular Examples Comparison
• Pros & Cons Comparison
• Framework Categories
• When Should You Use a Framework?
• When to Use What?
• Vanilla JS vs Framework
• Real-World Analogy
• Current Trends & Recommendations
• Interview Q&A
• Interview MCQ

What Are JavaScript Frameworks?

A JavaScript framework is a pre-built collection of JavaScript code, libraries, and tools that provides a structured foundation for building web applications. Instead of writing everything from scratch, developers use frameworks to handle common tasks like DOM manipulation, state management, routing, and API communication.

Why Use JavaScript Frameworks?

Most Popular JavaScript Frameworks (2025)

1) React.js (Library, but framework-like)

// React component example
function Welcome({ name }) {
    const [count, setCount] = useState(0);
    return (
        <div>
            <h1>Hello, {name}!</h1>
            <button onClick={() => setCount(count + 1)}>
                Clicked {count} times
            </button>
        </div>
    );
}

2) Angular

// Angular component example
@Component({
    selector: 'app-welcome',
    template: `
        <h1>Hello, {{name}}!</h1>
        <button (click)="increment()">
            Clicked {{count}} times
        </button>
    `
})
export class WelcomeComponent {
    name = "World";
    count = 0;
    increment() { this.count++; }
}

3) Vue.js

<!-- Vue component example -->
<template>
    <div>
        <h1>Hello, {{ name }}!</h1>
        <button @click="count++">
            Clicked {{ count }} times
        </button>
    </div>
</template>

<script>
export default {
    data() {
        return { name: "World", count: 0 }
    }
}
</script>

4) Svelte

<!-- Svelte component example -->
<script>
    let name = "World";
    let count = 0;
</script>

<h1>Hello, {name}!</h1>
<button on:click={() => count++}>
    Clicked {count} times
</button>

5) Next.js (React Framework)

6) Nuxt.js (Vue Framework)

Framework Comparison Table

*Svelte compiles away; no runtime framework layer is shipped in the same way as traditional frameworks.

Library vs Framework

Popular Examples Comparison

JavaScript / Web Development

Backend / Python and Beyond

Pros & Cons Comparison

Framework Categories

Full-Featured Frameworks

• Angular - complete solution (routing, forms, HTTP, testing)
• Ember.js - convention over configuration

UI Libraries (often paired with tools)

• React - focuses on view layer
• Preact - lightweight React alternative
• Solid - fine-grained reactivity

Progressive Frameworks

• Vue.js - drop-in script or full framework
• Alpine.js - lightweight and simple

Compiler-based

• Svelte - compiles to vanilla JavaScript
• Qwik - resumable architecture

Meta-Frameworks

• Next.js (React + SSR/SSG)
• Nuxt.js (Vue + SSR/SSG)
• Remix (React + full-stack)
• Astro (multi-framework islands architecture)

When Should You Use a Framework?

When to Use What?

Vanilla JavaScript vs Framework Comparison

// VANILLA JS (without framework)
const button = document.querySelector('#myButton');
const countSpan = document.querySelector('#count');
let count = 0;

button.addEventListener('click', () => {
    count++;
    countSpan.textContent = count;
});

// React (with framework)
function Counter() {
    const [count, setCount] = useState(0);
    return (
        <>
            <span>{count}</span>
            <button onClick={() => setCount(count + 1)}>+</button>
        </>
    );
}

Real-World Analogy

BUILDING A HOUSE ANALOGY

LIBRARY = Tool Shed
- You decide design, structure, and materials
- You pick tools as needed (e.g., Axios, Lodash, D3)
- You are the general contractor
- Tools do not dictate the full architecture

FRAMEWORK = Prefab Home Kit
- Comes with pre-defined foundation and structure
- You customize inside that structure
- The framework guides architecture and conventions
- Faster for standard app patterns with teams

Current Trends & Recommendations (2025)

10 JavaScript Frameworks Interview Q&A

10 JavaScript Frameworks MCQs