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Athithya Sivasankarar
Athithya Sivasankarar

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JavaScript Basics

#javascript #beginners #codenewbie #programming

JavaScript is one of the most important programming languages used in web development.
It helps make websites interactive and dynamic.

we will understand:

  • What is JavaScript
  • Data Types in JavaScript
  • Difference between Primitive and Non-Primitive
  • Variables in JavaScript

1. What is JavaScript?

JavaScript is a versatile, dynamically typed programming language that brings life to web pages by making them interactive. It is used for building interactive web applications, supports both client-side and server-side development, and integrates seamlessly with HTML, CSS, and a rich standard library.

  • JavaScript is a single-threaded language that executes one task at a time.

  • It is an interpreted language which means it executes the code line by line.

  • The data type of the variable is decided at run-time in JavaScript, which is why it is called dynamically typed.

Example 

<html>
<head></head>
<body>
    <h1>Check the console for the message!</h1>
    <script>
        console.log("Hello, World!");
    </script>
</body>
</html>
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Output:

Hello World

2. Data Types in JavaScript

What is a Data Type?

A data type defines what kind of value a variable holds (number, text, etc.).

JavaScript is dynamically typed, meaning you don’t need to define the type manually.

Types of Data in JavaScript

According to W3Schools, JavaScript has 8 data types:

Primitive Data Types (7 types)

1. Number 

let x = 10;
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2. String 

let name = "Athithya";
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3. Boolean 

let isStudent = true;
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4. Undefined 

let a;
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5. Null 

let value = null;
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6. BigInt 

let big = 12345678901234567890n;
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7. Symbol 

let id = Symbol("id");
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These are called primitive because they store a single value.

Non-Primitive Data Type

Object 

let person = {
  name: "Athithya",
  age: 21
};
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Objects can store multiple values (key-value pairs).

Difference Between Primitive and Non-Primitive

Feature Primitive Non-Primitive
Type Basic data Complex data
Storage Single value Multiple values
Mutability Immutable Mutable
Examples Number, String Object, Array
Memory Stored directly Stored by reference

Example 

// Primitive
let a = 10;
let b = a;
b = 20;

console.log(a); // 10

// Non-Primitive
let obj1 = {name: "A"};
let obj2 = obj1;
obj2.name = "B";

console.log(obj1.name); // B
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Primitive → value is copied
Non-Primitive → reference is copied

3. Variables in JavaScript

What is a Variable?

A variable is a container used to store data values.

Ways to Declare Variables

1. var 

var x = 10;
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  • Old method
  • Function scoped

2. let 

let y = 20;
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  • Block scoped
  • Can be updated

3. const 

const z = 30;
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  • Cannot be reassigned
  • Must be initialized

Example 

let name = "Athithya";
let age = 21;
const country = "India";

console.log(name, age, country);
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Output:

Athithya 21 India

typeof Operator

You can check data type using:

let x = "Hello";
console.log(typeof x);
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Output:

string

The typeof operator returns the type of a variable.

Reference

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