Variables in JavaScript: Declaration, Types, Scope

Declaring Variables: var, let, const

• var — function-scoped, can be redeclared and updated, hoisted with undefined.
• let — block-scoped, can be updated but not redeclared in the same scope.
• const — block-scoped, cannot be updated or redeclared; must be initialized at declaration.

var x = 10;
let y = 20;
const z = 30;

Scope of Variables

• Global scope — declared outside any function, accessible everywhere.
• Function scope — declared with var inside a function, accessible only within it.
• Block scope — declared with let/const inside { }, accessible only within that block.