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Introduction to JavaScript

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Constant 2/3

Block Scope of Constants

Declaring a variable with the const keyword is similar to declaring a variable with the let keyword when it comes to Block Scope, for example.

The personName declared in the block, in this example, is not the same as the personName declared outside the block:


              
12345

            
const  personName = "Mike";
if (2 > 1){
    const  personName = "Smith";
}
console.log(personName)
copy

We gave you a good understanding of block-scope but it is not a good practice to use the same name inside and outside the code block.

Constants are Assigned Values at the time of Declaration

In JavaScript, we can initialize variables in one line and assign them values in the next line with the let and the var keywords but we cannot do that with the const keyword, and if we do so, we get an error, for example.


              
123456

            
let  age;
age = 23;
console.log(age)
var  height;
height = 5;
console.log(height);
copy

But with const we get an error.


              
123

            
const  PI;
PI = 3.14159265359;
console.log(PI);
copy
Uppgift

Swipe to start coding

A constant variable named gravity has been given to you. But it cannot be displayed due to some error. Your task is to make changes in the code so that it can be displayed properly.

Lösning

Switch to desktopByt till skrivbordet för praktisk övningFortsätt där du är med ett av alternativen nedan
Var allt tydligt?

Hur kan vi förbättra det?

Tack för dina kommentarer!

Avsnitt 3. Kapitel 10

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book
Constant 2/3

Block Scope of Constants

Declaring a variable with the const keyword is similar to declaring a variable with the let keyword when it comes to Block Scope, for example.

The personName declared in the block, in this example, is not the same as the personName declared outside the block:


              
12345

            
const  personName = "Mike";
if (2 > 1){
    const  personName = "Smith";
}
console.log(personName)
copy

We gave you a good understanding of block-scope but it is not a good practice to use the same name inside and outside the code block.

Constants are Assigned Values at the time of Declaration

In JavaScript, we can initialize variables in one line and assign them values in the next line with the let and the var keywords but we cannot do that with the const keyword, and if we do so, we get an error, for example.


              
123456

            
let  age;
age = 23;
console.log(age)
var  height;
height = 5;
console.log(height);
copy

But with const we get an error.


              
123

            
const  PI;
PI = 3.14159265359;
console.log(PI);
copy
Uppgift

Swipe to start coding

A constant variable named gravity has been given to you. But it cannot be displayed due to some error. Your task is to make changes in the code so that it can be displayed properly.

Lösning

Switch to desktopByt till skrivbordet för praktisk övningFortsätt där du är med ett av alternativen nedan
Var allt tydligt?

Hur kan vi förbättra det?

Tack för dina kommentarer!

Avsnitt 3. Kapitel 10
Switch to desktopByt till skrivbordet för praktisk övningFortsätt där du är med ett av alternativen nedan
Vi beklagar att något gick fel. Vad hände?
some-alt