Зміст курсу

Introduction to JavaScript (staging)

1. Introduction

Writing our first code Output Using Variables 1/2 Output Using Variables 2/2

2. JavaScript syntax

JavaScript Syntax JavaScript Variables JavaScript Operators Identifiers in JavaScript Naming Identifiers Reserved keywords in JavaScript Naming Convention in JavaScript. Case Styles Variables Naming Convention Boolean Naming Convention Constant Naming Convention Function & Classes Naming Convention Multiline Strings Multiline Strings. Concatenating Commenting in JavaScript Commenting in JavaScript. Multi-line Comments

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.


              123
            
var number = 5;
var number = 3;
console.log(number);

But a variable declared with let does not allow redeclaration.


              123
            
let number = 5;
let number = 3; 
console.log(number);

Завдання

Swipe to show code editor

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.

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.


              123
            
planet = 'earth';
console.log(planet);
var planet;

But let does not allow hoisting.


              123
            
planet = 'earth';
console.log(planet);
let planet;

Summary:

let is the newer way to declare variables.
let has block scope.
let does not allow redeclaration.
let does not allow hoisting.

Перейдіть на комп'ютер для реальної практикиПродовжуйте з того місця, де ви зупинились, використовуючи один з наведених нижче варіантів

Все було зрозуміло?

Дякуємо за ваш відгук!

Секція 3. Розділ 8

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.


              123
            
var number = 5;
var number = 3;
console.log(number);

But a variable declared with let does not allow redeclaration.


              123
            
let number = 5;
let number = 3; 
console.log(number);

Завдання

Swipe to show code editor

Note: Solution-2 is not much preferable.

`let` Does Not Allow Hoisting


              123
            
planet = 'earth';
console.log(planet);
var planet;

But let does not allow hoisting.


              123
            
planet = 'earth';
console.log(planet);
let planet;

Summary:

let is the newer way to declare variables.
let has block scope.
let does not allow redeclaration.
let does not allow hoisting.

Все було зрозуміло?

Дякуємо за ваш відгук!

Секція 3. Розділ 8

Introduction to JavaScript (staging)

Let 2/2

let Does Not Allow Redeclaration

let Does Not Allow Hoisting

Summary:

Let 2/2

let Does Not Allow Redeclaration

let Does Not Allow Hoisting

Summary:

`let` Does Not Allow Redeclaration

`let` Does Not Allow Hoisting

`let` Does Not Allow Redeclaration

`let` Does Not Allow Hoisting