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Local vs Global Scope of Variables in JavaScript

Scope of Variables in Javascript

In this article, we will discuss the scope of variables in javascript which is local scope vs global scope. The scope indicates the “accessibility” and “visibility” of variables (i.e. life of a variable). Javascript variables are of local scope (function scope) or global scope.

Difference Between Local and Global scope

Local Scope Global Scope
Any variable declared inside a function is considered as in local scope. Any variable not declared inside a function is considered as in global scope.
It can be accessed only inside that function where it is declared.
Local variables will be available only in the function execution.
It can be accessed anywhere in the script
 That means local variables are created as soon as the control enters the function body and deleted as soon as the control exits the function body. Global variables will be available throughout the script execution

Example for the scope of the variable

var a = 10; //Global Scope

function display(){

document.write(" (global a =", this.a, "<br/>"); //a=10

var a= 20; // local Scope
document.write("local a =", a, "<br/>"); //a=20
}

display();

/*
Output:
global a =10
local a =20
*/

In the above code, the variable “a” has the value “10”, it is a global variable because this variable is not declared inside the function. Then we have a function display, inside the function, we print “a’ variable using this method. The “this” method is used to access an outside variable. And create another variable “a”, it is a local variable because this variable is declared inside the function. Then we print variable “a” and call the display() function. So, the output will display a=10, and a=20 because The variable ‘a’ has two values ​​10 and 20.

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