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

Var 2/3

Var Tolerate Redeclaration

Var tolerates the redeclaration. If a variable is declared with the same name twice with var we will not get an error, but with let we will get an error. For instance:


              12
            
let user = 'Mike';
let user = 'John';

But we can declare variables with the same names with var and the old values of the variables are simply overwritten, for example.


              123
            
var user = 'Mike';
var user = 'John';
console.log(user)

Завдання

Declare a variable company and assign the value " Apple". Redeclare the company and now set the value “Samsung” by using the var keyword. Show the updated value on the console.

Variable hoisting

Hoisting, in JavaScript, is a way where a function or a variable can be used before its declaration.
In JavaScript, var is hoisted while the let and const does not allow hoisting, for example.


              123
            
totalNumber = 10;
console.log(totalNumber);
var totalNumber;

If we use the variable inside console.log() and nothing is written before it we will get an undefined value. In JavaScript first, the memory is allocated to the variable and initially, their values are undefined after this they are assigned some values.


              12
            
console.log(company)
var company="panasonic";

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 5

Var 2/3

Var Tolerate Redeclaration

Var tolerates the redeclaration. If a variable is declared with the same name twice with var we will not get an error, but with let we will get an error. For instance:


              12
            
let user = 'Mike';
let user = 'John';

But we can declare variables with the same names with var and the old values of the variables are simply overwritten, for example.


              123
            
var user = 'Mike';
var user = 'John';
console.log(user)

Завдання

Declare a variable company and assign the value " Apple". Redeclare the company and now set the value “Samsung” by using the var keyword. Show the updated value on the console.

Variable hoisting


              123
            
totalNumber = 10;
console.log(totalNumber);
var totalNumber;


              12
            
console.log(company)
var company="panasonic";

Все було зрозуміло?

Дякуємо за ваш відгук!

Секція 3. Розділ 5

Var 2/3

Var Tolerate Redeclaration

Var tolerates the redeclaration. If a variable is declared with the same name twice with var we will not get an error, but with let we will get an error. For instance:


              12
            
let user = 'Mike';
let user = 'John';

But we can declare variables with the same names with var and the old values of the variables are simply overwritten, for example.


              123
            
var user = 'Mike';
var user = 'John';
console.log(user)

Завдання

Declare a variable company and assign the value " Apple". Redeclare the company and now set the value “Samsung” by using the var keyword. Show the updated value on the console.

Variable hoisting


              123
            
totalNumber = 10;
console.log(totalNumber);
var totalNumber;


              12
            
console.log(company)
var company="panasonic";

Все було зрозуміло?

Дякуємо за ваш відгук!

Var Tolerate Redeclaration

Var tolerates the redeclaration. If a variable is declared with the same name twice with var we will not get an error, but with let we will get an error. For instance:


              12
            
let user = 'Mike';
let user = 'John';

But we can declare variables with the same names with var and the old values of the variables are simply overwritten, for example.


              123
            
var user = 'Mike';
var user = 'John';
console.log(user)

Завдання

Declare a variable company and assign the value " Apple". Redeclare the company and now set the value “Samsung” by using the var keyword. Show the updated value on the console.

Variable hoisting


              123
            
totalNumber = 10;
console.log(totalNumber);
var totalNumber;


              12
            
console.log(company)
var company="panasonic";

Секція 3. Розділ 5