Learn JavaScript In Arabic 2021 - #068 - Scope - Block

Scope - Block

Study Plan:

Code & Notice:

Assignments:

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[mohamednomear]

Important note : a code block does not create a scope for "var" variable, but a function body does

[insafzrog]

هته الفيديوهات برعاية لو سالتك انت مصري حتقلي ايه 😂
منور يا استاذنا لك الامتنان والتقدير🥰

[Ayman-qmho]

Local scope: variable inside curly brackets {} or inside a function. Local Scope broken down into two different scopes:

- Block Scope: A variable when declared inside the IF or SWITCH conditions or inside FOR or WHILE loops,
are accessible within that particular condition or loop
- Function Scope: When a variable is declared inside a FUNCTION,
it is only accessible within that function and cannot be used outside that function.

[muneerseraj]

Global Scope: variables defined outside of any function or curly brackets are known as global variables and have global scope. Global scope means that the variables can be accessed from any part of that program, any function or conditional state can access that variable.

Local scope: variable inside curly brackets {} or inside a function. Local Scope broken down into two different scopes:

- Block Scope: A variable when declared inside the IF or SWITCH conditions or inside FOR or WHILE loops.
- Function Scope: When a variable is declared inside a FUNCTION.


var (Global and Function scope) doesn't have block scope.
* outside a function and curly brackets become GLOBAL scope. (Globale variable)
* inside a function, becomes FUNCTION scope. (local variable)

let (Global, Block, and Function scope)
* outside a function and curly brackets become GLOBAL scope. (Globale variable)
* outside a function, declared inside a { } becomes Block scope. (local variable)
* inside a function, becomes FUNCTION scope. (local variable)

var a =15; // Global Variable
if (2===2){
var a =10; //updated value for Global variable
}


function localVar(){
var a = 100; // Defined inside the function (Local variable)
console.log(`localvar Function Scope = ${a}`);
}


function localVarbyparm(a) {
a++; // Function variable (Local variable)
console.log(`localVarbyparm Function Scope = ${a}`);
}

function takeGlobalvar(){
a=200; //updated value for Global variable
//(took the global variable a from outside the function because the function doesn't have variable a)
}

console.log(`Global Scope after update= ${a}`);

localVar();

console.log(`Global Scope = ${a}`);

localVarbyparm(a);
console.log(`Global Scope = ${a}`);

takeGlobalvar();
console.log(`Global Scope after takeGlobalvar function = ${a}`);


result:
Global Scope after update= 10
localvar Function Scope = 100
Global Scope = 10
localVarbyparm Function Scope = 11
Global Scope = 10
Global Scope after takeGlobalvar function = 200


let



let a =15; // Global Variable
if (2===2){
let a =10; //Defined inside the block (Local variable)
}


function localVar(){
let a = 100; // Defined inside the function (Local variable)
console.log(`localvar Function Scope = ${a}`);
}


function localVarbyparm(a) {
a++; // Function variable (Local variable)
console.log(`localVarbyparm Function Scope = ${a}`);
}


function takeGlobalvar(){
a=200; //updated value for Global variable
//(took the globle variable a from outside the function because the function doesn't have variable a)
}

console.log(`Global variable did not update after IF block = ${a}`);

localVar();
console.log(`Global Scope = ${a}`);
localVarbyparm(a);
console.log(`Global Scope = ${a}`);
takeGlobalvar();
console.log(`Global varable updated in function takeGlobalvar = ${a}`);

result:
Global variable did not update after IF block = 15
localvar Function Scope = 100
Global Scope = 15
localVarbyparm Function Scope = 16
Global Scope = 15
Global varable updated in function takeGlobalvar = 200

[FartakaTechnology]

عظمة كالعادة يا بشمهندس
ربنا يوفقك ويجزاك خير علي الي بتقدمه للناس من علم بكل حب
هفضل احطلك الكومنت دا علي كل فيديو اذاكره في الكورس دا لحد ما يخلص كله

[AhmedMahmoudMMD]

السلام عليكم ورحمة الله وبركاته : اللي عنده مشكلة في الفيديو لازم اهم حاجة يكون عارف المعلومتين دول وهتتحل باذن الله :
: 1
// Note : Remember that when you declare a variable with let or const keywords
// in a specific block(if, while, ...),
// the variable's value will only be accessible in this scope
// But if you declare it with the var, you will be able to access it from anywhere

: 2
// Important Note: Blocks do not create a scope for variables declared with the var
// keyword, but functions do.

[gamersyriapubgmobile]

جزاك الله خيرا يا بشمهندس و شكرا على هذا المجهود الرائع
زادك الله علمًا ورفعك قدرًا و جعل هذا العلم النافع فى ميزان حسناتك💗

[mohammedmagdy]

الله يوفقك يا استاذ اسامة شرحك اكثر من رائع

[fpistories]

ال انا فهمته ان لو انا بستخدم function مش هيبقى فى خطر اوى لو انا استخدمت ال let او var علشان كدة كدة مش هعرف اوصل للمتغير ال جوا لو انا هستخدمه بره
لكن فى حالة ال if او switch او for لازم اخد بالى علشان ممكن اوصل للمتغير الجوا واستخدمه بره علشان كدة لازم استخدم let علشان تمنع الحكاية ديه و يبقى المتغير ال جوا خاص بالجوا

[Ahmed_Abdelaziz_Mohamed]

ممكن يا باشمهندس تمنع اعلانات المقاطعة عندك ؟

[mahjoubhabbachi]

let table = [1, 2, 3]

for(let i = 0 ; i<table.length ; i++){
var tab = new Array(3);
tab[i] = table[i] + table[i]
}

console.log(tab)
ya bach mohandech law sama7et tfahemni lih lconsole beyedili natiga di

[moazahmed]

طيب سوال ؟
في الدرس الفات لما عملنا كونسول لوق = جانا القلوبال اول بعده اللوكال مع انو حسب الانحنا متعلمينو انو الكومبايلر بيقرا الكود بالترتيب الاول ثم الذي يليه ثم الذي يليه ....يلا في الدرس ده اطبع النست اول ثم القلوبال ...ي ريت القا اجابه
شكرا

[naserhazzaa]

استاذ لما استخدمنا الفار ... الفانكشن ماعملت اوفر رايد بينما الشرط عملت اوفر رايد ممكن توضيح بعد اذنك

[A-h-m-e-d_S-a-m-y]

عندى سؤال
ليه مش بتستخدم let&const علطول بدل var ؟

[aliqawash]

الله يسامحك رحت اشوف اش هيا هاد
لو سالتك انت مصري تقولي ايه 😆