Understanding Variables and Data Types in JavaScript

Understanding Variables and Data Types in JavaScript

Before diving deeper into JavaScript, it’s important to understand variables and data types. These are the building blocks of any programming language.

What are Variables?

Variables are like containers that store data values. You can think of them as boxes with labels where you keep different kinds of information.

Declaring Variables

In JavaScript, we can declare variables using three keywords: var, let, and const.

// Example:
var name = "Lokesh";
let age = 25;
const country = "India";

• var: Used in older JavaScript code. It has function scope and can be re-declared.
• let: Introduced in ES6, it has block scope and cannot be re-declared in the same scope.
• const: Also introduced in ES6, used for variables whose values never change.

JavaScript Data Types

JavaScript has two main categories of data types:

1. Primitive Data Types

• String
• Number
• Boolean
• Null
• Undefined
• Symbol (ES6)
• BigInt (ES11)

// Examples:
let name = "Lokesh";      // String
let age = 25;             // Number
let isStudent = true;     // Boolean
let value = null;         // Null
let city;                 // Undefined

2. Non-Primitive (Reference) Data Types

• Object
• Array
• Function

// Examples:
let person = { name: "Lokesh", age: 25 };   // Object
let colors = ["red", "green", "blue"];      // Array
function greet() { console.log("Hello!"); } // Function

Important Notes:

• JavaScript is a dynamically typed language — you don’t need to declare the data type of a variable.
• You can reassign variables (except const).
• Use let and const instead of var for modern code.

Summary

Understanding variables and data types is the first major step in mastering JavaScript. In the next part, we’ll explore Operators and Expressions — how to perform calculations and make decisions in your code.

Stay tuned and keep coding 💻