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var vs let vs const

Discussion on different types of declaration

Ragav Kumar V

Ragav Kumar V

Aug 21, 2022 — Updated Sep 23, 2022 · 2 min read

Redeclaration

Declaration means creating a variable
Redeclaration means re-creating a variable

var x1 = 10;
let x2 = 20;
const x3 = 30;
var x1 = 80; // - ✅ Allowed
let x2 = 70; // - ❌ Error
const x3 = 90; // - ❌ Error

Reassignment

Changing the value of the variable

var x1 = 10;
let x2 = 20;
const x3 = 30;
x1 = 180; // - ✅ Allowed
x2 = 170; // - ✅ Allowed
x3 = 190; // - ❌ Error

const - exception

Our exceptation might be wrong about const since we must embrace how JS works
We object/array is declaraed with const inside value could be modified

const player = {
  name: "Gukesh D",
  game: "chess",
  age: 16,
  rating: 2699,
  title: "Grandmaster",
};
player.rating = 2710; // - ✅ Allowed
console.log(player);
// Output
{
  name: "Gukesh D",
  game: "chess",
  age: 16,
  rating: 2710,
  title: "Grandmaster",
};
player = 10; // - ❌ Error

const movies = ["Vikram", "KGF", "RRR", "Valimai"];
movies[1] = "Master"; // - ✅ Allowed
console.log(movies);
// Output
// ["Vikram", "Master", "RRR", "Valimai"]
movies = "cool"; // - ❌ Error

@ragavkumarv

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