Difference Between Var, Let, Const In JavaScript

Var

Var creates a variable that is function-scoped and can be reassigned at any time. If a var variable is declared outside of a function, it is part of the global scope and will be a property on the global object.

Example

//Example 1
var language = "javascript";
language = "JavaScript is the world's most popular programming language"; // New Value Assigned
console.log(language);
//Output
//JavaScript is the world's most popular programming language
//Example 2
function LanguageExample() {
    var likes = 500;
    console.log(likes); //Output:- 500
}
console.log(likes); //ReferenceError: likes is not defined (we can not access outside the function . only accessible inside function)

Let

A variable declared with let can be reassigned at any time. let is block scoped, which means it is only available within the function.

Example

function LanguageExample() {
    let likes = 500;
    console.log(likes); //Output:- 500
}
console.log(likes); //ReferenceError: likes is not defined (Unable to access outside the function block)

const

const is used for constant values. Hence, they cannot be reassigned. They are block scoped, just like let.

Example

// Example 1
const language = "javascript";
language = "JavaScript is the world's most popular programming language"; // Uncaught TypeError: Assignment to constant variable.
//Example 2
function LanguageExample() {
    const likes = 500;
    console.log(likes); //Output:- 500
}
console.log(likes); //ReferenceError: likes is not defined