⚡ var vs let vs const + Hoisting

🔹 1. var

• Function scoped (or globally scoped if declared outside a function)
• Can be redeclared and updated.
• Hoisted : moved to top of scope but initialized as undefined.
• Example:

    console.log(a)      // undefined (hoisted, but not initialized yet)
    var a = '10'
    console.log(a)      // a = '10'

🔹 2. let

• Block scoped (inside braces)
• Can be updated ,but not redeclared in the same scope.
• Hoisted but in Temporal Dead Zone (TDZ) -> Can’t access before declaration.
• Example:

    // console.log(a)       // ❌ ReferenceError (TDZ)
    let a = 10
    console.log(a)          // 20

🔹 3. const

• Block scoped
• Must be initialized at declaration.
• Can’t be reassigned (but objects/arrays can still be mutated).
• Example:

    // const a      // ❌ Error
    const c = 20
    // c = 10          // ❌ TypeError
    const arr = [1,3]
    arr.push(2)
    console.log(arr)        // [1,3,2]

🔹 4. Hoisting Summary

• var -> Hoisted + “initialized as undefined”
• let/const -> Hoisted but in TDZ (cannot access until declared).

👉 Interview One-liner:

“var is a function scoped and hoisted with undefined. let and const are block scope and hoisted but not until initialized(TDZ). const required initializaton and cannot be reassigned.”