Variables In Java Script

What is a Variable?
In JavaScript, a variable is a container used to store data values so you can use and manipulate them in your program.
A variable is like a labeled box where you keep information. You give it a name and assign it a value.

Yes, in JavaScript we mainly have 3 types of variables:

1. var
   Features:
   Function-scoped (works inside a function)
   Can be redeclared
   Can be updated
   Hoisted (moves to top, but value = undefined)
   Example:
var x = 10;
var x = 20; // ✅ allowed
   Problem: Can create bugs because it ignores block {} scope

2. let
   Features:
   Block-scoped (works inside { })
   Can be updated
   Cannot be redeclared in same scope
   `Example:
   let y = 10;
   y = 20; // allowed

let y = 30; // error`
Safer than var

3.const
Features:
Block-scoped
Cannot be updated
Cannot be redeclared
Must assign value when declaring
Example:
const z = 10;
z = 20; // ❌ error

Biggest Difference → SCOPE
What is scope?
Scope means where you can use the variable
*var (ignores block {})
if (true) {
var x = 10;
}
console.log(x); // Works
Even though it's inside {}, you can still use it outside
That’s why var is unsafe.

*let (respects block {})
f (true) {
let y = 20;
}
console.log(y); // Error
Only works inside {}
Safer and better

*const (same as let)
if (true) {
const z = 30;
}
console.log(z); // Error

• What is Variable Declaration? Declaration means creating a variable (just naming it) You are telling JavaScript: “I will use this variable” let x; Here: Variable name = x No value assigned yet So: Declaration = create variable, no value

*What is Variable Initialization?
Initialization means giving a value to the variable
x = 10;
Now:
x has value 10
So:
Initialization = assigning value

*Declaration + Initialization Together?
Most of the time we do both in one line:
let x = 10;
This means:
Declared variable x
Initialized with value 10.