My JavaScript learning journey—basic concepts.

Data Types, Variables, Functions, Return, Arguments/Parameters, Function Calling & Concatenation.

1. Data Types - Number, String, Boolean, Undefined, Null, Symbol, BigInt.

Number - Numeric values (integers, floats) - let age = 25;
String - Text data - let name = "John";
Boolean - True or False - let isOnline = true;
Undefined - A variable declared but not assigned a value -let x;
Null - Represents an intentional "no value"- let data = null;
Symbol - Unique and immutable value - let id = Symbol("id");
BigInt - For very large numbers - let big = 12345678901234567890n;

1. Variables

var Old way (not recommended now) ✅ Yes

let Modern way (use for values that may change) ✅ Yes
const Use for fixed values (won’t change) ❌ No

1. Using let let age = 25; age = 26; // ✅ Can change

2.Using const
const pi = 3.14;
// pi = 3.14159; ❌ Error: Cannot reassign a const variable

3.Using var (old style)
var name = "Alice";
name = "Bob";

What is a Function in JavaScript?
A function is a block of code designed to perform a task.
You can reuse it whenever needed.

👉 Think of it as a machine that does a specific job when called.
Syntax:
function functionName(parameters) {
// code to execute
}
✅ functionName – name of the function
✅ parameters – values you pass to the function (optional)

✅ Simple Example:

function greet() {
console.log("Hello, welcome!");
}

greet(); // Calling the function

• Function with Parameters

function greetUser(name) {
console.log("Hello, " + name + "!");
}

greetUser("Jeevananthan"); // Output: Hello, Jeevananthan!

• Function that Returns a Value

function add(a, b) {
return a + b;
}

let result = add(5, 3);
console.log(result); // 8

🔶 What is concatenation?
Concatenation means joining two or more strings together.

🔹 Using + Operator (Most Common Way)

let firstName = "Jeevananthan";
let lastName = "Annadurai";

let fullName = firstName + " " + lastName;
console.log(fullName); // Jeevananthan Annadurai
✅ " " (space in quotes) is added between names for spacing.

🔹 Concatenating with Numbers
JavaScript converts numbers to strings when using + with text:

let age = 25;
let text = "I am " + age + " years old.";
console.log(text); // I am 25 years old.

Quick Summary

✅ 1. Data Types
JavaScript has:

Primitive types like string, number, boolean, null, undefined, symbol, and bigint

Non-primitive types like object, array, and function.

✅ 2. Variables
Use let for values that can change.

Use const for values that shouldn’t change.

Avoid var unless you're dealing with older code.

✅ 3. Functions
Functions are reusable blocks of code.

Use parameters to pass data in.

Use return to send a result back.

Arrow functions (=>) make your code shorter and modern.

✅ 4. Concatenation
Used to join strings together.

Use + or += for basic joining.

Use template literals (Hello, ${name}) for cleaner, more readable code.

Thank you for reading my blog. Let's get connected if you have any questions regarding these topics. Have a good day!! Bye see ya...