What is JavaScript?
JavaScript is a high-level, interpreted scripting language primarily used to add interactivity and dynamic behavior to websites. It is supported by all modern browsers and can also run outside the browser using Node.js.
JavaScript is one of the core technologies of the web, alongside HTML and CSS. While HTML gives structure and CSS styles the page, JavaScript makes it interactive — like handling button clicks, validating forms, displaying animations, and more.
Why Learn JavaScript?
- It's the most popular language for web development.
- You can build both front-end and back-end apps (using Node.js).
- It's beginner-friendly and has a huge community.
- All browsers understand JavaScript by default (no installation needed).
Real-World Analogy
Think of a website like a robot:
HTML is its body,
CSS is the clothes and colors,
JavaScript is the brain that makes it move and respond.
Key Characteristics
- Dynamic and loosely typed
- Supports object-oriented, functional, and imperative styles
- Interpreted (no compiler needed)
- Event-driven and asynchronous capabilities (via Promises, async/await)
Why is JavaScript Considered Interpreted?
JavaScript is traditionally known as an interpreted language because:
- It executes code line-by-line without needing a compiler.
- Browsers like Chrome and Firefox directly interpret it using engines like V8.
- It works dynamically, allowing type changes at runtime.
However, modern JavaScript engines now use JIT (Just-In-Time) compilation to improve performance — so JavaScript today is actually a hybrid of interpreted and compiled behavior.
Real Use Cases
- Form validation
- Interactive maps (like Google Maps)
- Real-time updates (like chat apps or notifications)
- Games and animations on the browser
Beginner Practice Task
Create a simple HTML page with a button that shows an alert saying "Hello, JavaScript!" when clicked.
<button onclick="alert('Hello, JavaScript!')">Click Me</button>Interview Question
Q: Why is JavaScript called a "loosely typed" or "dynamically typed" language?
A: Because you don’t need to declare variable types. A variable can hold any type and change at runtime:let x = 5; x = "hello";
🧠 Quick Quiz
- What type of language is JavaScript (compiled or interpreted)?
- Can JavaScript run outside the browser?
- What are three main parts of a website?
What is JavaScript?
JavaScript is a high-level, interpreted scripting language primarily used to add interactivity and dynamic behavior to websites. It is supported by all modern browsers and can also run outside the browser using Node.js.
JavaScript is one of the core technologies of the web, alongside HTML and CSS. While HTML gives structure and CSS styles the page, JavaScript makes it interactive — like handling button clicks, validating forms, displaying animations, and more.
Why Learn JavaScript?
- It's the most popular language for web development.
- You can build both front-end and back-end apps (using Node.js).
- It's beginner-friendly and has a huge community.
- All browsers understand JavaScript by default (no installation needed).
Real-World Analogy
Think of a website like a robot:
HTML is its body,
CSS is the clothes and colors,
JavaScript is the brain that makes it move and respond.
Key Characteristics
- Dynamic and loosely typed
- Supports object-oriented, functional, and imperative styles
- Interpreted (no compiler needed)
- Event-driven and asynchronous capabilities (via Promises, async/await)
Why is JavaScript Considered Interpreted?
JavaScript is traditionally known as an interpreted language because:
- It executes code line-by-line without needing a compiler.
- Browsers like Chrome and Firefox directly interpret it using engines like V8.
- It works dynamically, allowing type changes at runtime.
However, modern JavaScript engines now use JIT (Just-In-Time) compilation to improve performance — so JavaScript today is actually a hybrid of interpreted and compiled behavior.
Real Use Cases
- Form validation
- Interactive maps (like Google Maps)
- Real-time updates (like chat apps or notifications)
- Games and animations on the browser
Beginner Practice Task
Create a simple HTML page with a button that shows an alert saying "Hello, JavaScript!" when clicked.
<button onclick="alert('Hello, JavaScript!')">Click Me</button>Interview Question
Q: Why is JavaScript called a "loosely typed" or "dynamically typed" language?
A: Because you don’t need to declare variable types. A variable can hold any type and change at runtime:let x = 5; x = "hello";
🧠 Quick Quiz
- What type of language is JavaScript (compiled or interpreted)?
- Can JavaScript run outside the browser?
- What are three main parts of a website?