JavaScript Moderne - Variables et Scope globale (Let & Const vs Var)

Javascript moderne (ES6 - ES11) #16 Variables et Scope globale (Let & Const vs Var) [Tuto fr]
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Le code source : https://github.com/drcmind/Javascript-Moderne


les amis dans cette nouvelle série de vidéos on va apprendre ensemble le langage de programmation Javascript depuis sa version ECMA2015 jusqu’à ECMA2020 (ES6 - ES11) et delà on se focalisera beaucoup sur la notion de :

  1. Let et Const
  2. Arrow function
  3. Object literal
  4. Template String
  5. Destructuring assignment
  6. Default parameter
  7. Rest et Spread operators
  8. Class, Modules, Promises, iterators
  9. Await/Async
  10. Map et Set

#javascript #programming #web-development #developer

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JavaScript Moderne - Variables et Scope globale (Let & Const vs Var)
Dexter  Goodwin

Dexter Goodwin

1623916080

A Simple Explanation Of JavaScript Variables: Const, Let, Var

The variable is a fundamental concept that any developer should know.

In JavaScript, constlet, and var are the statements you can declarate variable.

I’m going to describe each variable type around the declaration, initialization, value access, and assignment. Each of the 3 types (constlet, and var) create variables that behave differently exactly in these 4 steps.

This post isn’t quite beginner friendly, but rather useful to solidify your knowledge of variables and their behavior.

Let’s get started.

1. Variable identifier

First, let’s understand what a variable is.

In simple terms, a variable is a placeholder (or a box) for a value. A value in JavaScript can be either a primitive value or an object.

The variable has a name, which stricter is called identifier. Examples of identifiers are myNumbernamelistitem.

The syntax of an identifier is pretty simple:

An identifier can contain letters, digits 0..9, and special symbols $_. An identifier cannot start with a digit 0..9.

Examples of valid identifiers are myNumbermy_numberlist1$item_nameab$_.

#javascript #variable #const #let #var

Coy  Roberts

Coy Roberts

1601976360

Javascript let vs var: The Difference and Comparison

Javascript let, and var are both used for variable declaration. Before the ES6, JavaScript had only two types of scope:

  1. Global Scope
  2. Function Scope

Global Scope

Variables that are declared Globally (outside any function) have Global Scope.

var netflixFilm = "enola holms";

// code here can use netflixFilm

function detective() {
  // code here can also use netflixFilm
}

In this example, the variable is defined outside the function. So it is in the global scope.

You can access global variables anywhere in JavaScript programs.

#javascript #javascript let #javascript let vs var

Eldora  Bradtke

Eldora Bradtke

1589938080

JavaScript Variables: var and let and const

There are three ways to create variables in a JavaScript application: using var, using let, or using const. This will not be a post trying to convince you which one you should use, or arguing about what is best. It’s just good to know about the differences and what it means when you use the different options. But hopefully by the end of all this you’ll be comfortable with the three options and can make a decision for your team that will suit your needs. To get the most out of this post, it is best if you understand variable scope, which we covered in this post previously.

#javascript #var #let #const

Eldora  Bradtke

Eldora Bradtke

1593862020

JavaScript Variables Explained. Var, Let and Const with examples.

Before the arrival of ES6 or EcmaScript 6 released in 2015, as a Javascript developer, you could only declare variables using the var keyword.
Now things has changed and two new keywords have been introduced to meet the developers needs who felt the old one way solution very tight for the modern web app requirements.
In this article I will try to explain you in the simplest way possible, the differences between var, let and const type variables.
I think the best way to do this is to try to extrapolate the essence of their nature by describing them in few words followed by examples which gives you the confirmation and consolidation of what you learned in the theory.
Like many other programming languages, JavaScript has variables. I talk you through var, let and const, and how they differ from each other with the use of some simple examples.

#javascript #var #let #const #programming

JavaScript Var, Let, and Const - 8

To declare a variable in JavaScript either var, let or const is used.
We will distinguish between the three with the following features:

  • Block scope
  • Update and redeclaration
  • Hoisting
  • Undefined

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#javascript #javascript var #let #const