Notice: This page requires JavaScript to function properly.
Please enable JavaScript in your browser settings or update your browser.Aprende Let 2/2 | Data Types and Variables
Introduction to JavaScript

book
Let 2/2

let Does Not Allow Redeclaration

Redeclaration means declaring a variable again. As discussed in the previous chapter, we can redeclare the variable again and again with var but we cannot do that with the let keyword.

var number = 5;
var number = 3;
console.log(number);

              
123

            
var number = 5;
var number = 3;
console.log(number);
copy

But a variable declared with let does not allow redeclaration.

let number = 5;
let number = 3;
console.log(number);

              
123

            
let number = 5;
let number = 3; 
console.log(number);
copy
Tarea

Swipe to start coding

A variable named country with two values Pakistan and England has been given declared for you using the let keyword but this code won’t run because let doesn’t allow redeclaration. Your task is to make changes in the below code so that we England as the output. There are two possible ways to do get the desired result.

Solución

let country = "Pakistan";
country = "England";
console.log(country);
//OR
//var country = "Pakistan";
//var country = "England";
//console.log(country);

Note: Solution-2 is not much preferable.

let Does Not Allow Hoisting

As discussed in the previous chapter, let does not allow hoisting i.e. we cannot use a variable before the declaration. Variables declared with the var keyword can be accessed or used before the declaration, for example.

planet = 'earth';
console.log(planet);
var planet;

              
123

            
planet = 'earth';
console.log(planet);
var planet;
copy

But let does not allow hoisting.

planet = 'earth';
console.log(planet);
let planet;

              
123

            
planet = 'earth';
console.log(planet);
let planet;
copy

Summary:

  • let is the newer way to declare variables.

  • let has block scope.

  • let does not allow redeclaration.

  • let does not allow hoisting.

¿Todo estuvo claro?

¿Cómo podemos mejorarlo?

¡Gracias por tus comentarios!

Sección 3. Capítulo 8
let country = "Pakistan";
let country = "England";

Pregunte a AI

expand
ChatGPT

Pregunte lo que quiera o pruebe una de las preguntas sugeridas para comenzar nuestra charla

some-alt