Updated on 12 Sep 2022 | 3 Min Read
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With JavaScript, the user can declare variables with three keywords, which are let, var, and const. The terms var let and const are somewhat confusing. We will explain all 3 variables with the help of examples.

The difference between the variables var, let as well as const is described below in different ways.

  • Scope
  • Hoisting
  • Reassign the value
  • Redeclaration of the variable

1. Scope

var let const
It's a function scope block scope block scope
Function scope example

const func = () => {
    var val1 = 5;
    if(true) {
        var val2 = 10;
        console.log(val1); //Output 5
        console.log(val2); //Output 10
    }
}
func();
console.log(val1); //undefined. Not available outside function
console.log(val2); //undefined. Not available outside function

Block scope example

const func = () => {
    let x = 10;
    if(x === 10) {
        let y = 20;
        console.log(x); //Output 10
        console.log(y); //Output 20
    }
    console.log(x); // Output 10
    console.log(y); // ’undefined'
}
func();

2. Hoisting

Hoisting is the term used to define a variable prior to its declaration.

var let const
Allowed Not allowed Not allowed
var1 = 100; 
console.log(var1);
var var1;
// 100		 let1 = 100; 
console.log(let1);
let let1;
// ReferenceError: let1 is not defined		 const1 = 100; 
console.log(const1);
const const1;
// SyntaxError: Missing initializer in const declaration

3. Reassign the value

var let const
Allowed Allowed Not allowed

4. Redeclaration the value

var let const
Allowed Not Allowed Not allowed