Please enable Javascript to correctly display the contents on Dot Net Tricks!

Understanding Local and Global Variables in JavaScript

 Print 
  Author : Shailendra Chauhan
Posted On : 22 Sep 2013
Total Views : 22,957   
Updated On : 24 Sep 2013
 

Like other programming languages, JavaScript also has local and global variables. But the declaration and scope of a variable in JavaScript is different from others programming languages. In this article, I am going to explain the difference between local and global variables in JavaScript.

Types of Variables in JavaScript

  1. JavaScript Local Variable

    A variable that is declared inside a function definition is called local and has scope to that function only. JavaScript does not support block scope in which a set of curly braces {. . .} defines a new scope.

    <script>
    // Global variable.
    var a = "Dot Net Tricks !";
    function Show() {
     // A local variable is declared in this function.
     var a = "Hello World !";
    
     alert("Value of 'a' inside the function " + a); //Hello World !
    }
    
    alert("Value of 'a' outside the function : " + a); //Dot Net Tricks !
    </script>
    
  2. JavaScript Global Variable

    A variable that is declared outside of a function definition is called a global variable and its scope is throughout your program means its value is accessible and modifiable throughout your program.

    <script >
    // Global variable.
    var a = "Dot Net Tricks !";
    function Show() {
     // A Local variable is declared in this function.
     var a = "Hello World !";
     alert("Value of 'a' inside the function :" + a); //Hello World !
    
     //b will have global scope
     b = "Hello JavaScript !";
     Display();
    }
    
    alert("Value of 'a' outside the function : " + a); //Dot Net Tricks !
    
    function Display() {
     //Since b variable has global scope
     alert("Value of 'b' outside the function : " + b); //Hello JavaScript !
    }
    </script>
    

Note

  1. A variable that is declared inside a function using the var keyword, will have a local scope.

  2. A variable that is declared inside a function without var keyword, will have a global scope means acts like a global variable.

What do you think?

I hope you will enjoy the tips while programming with JavaScript. I would like to have feedback from my blog readers. Your valuable feedback, question, or comments about this article are always welcome.



Free Interview Books
 
COMMENTS
20 JAN
ASP.NET Core with Angular4 (Online)
07:00 AM-09:00 AM IST / 07:30 PM Central Time
20 JAN
ASP.NET MVC with Angular (Classroom)
05:00 PM to 07:00 PM IST (+5:30 GMT)
20 JAN
ASP.NET MVC with Angular4 (Online)
03:00 pm to 05:00 pm
20 JAN
Angular2+4 with Firebase (Classroom)
03:00 PM to 05:00 PM IST (+5:30 GMT)
16 JAN
Developing Microsoft Azure Solutions (Online)
07:00 AM-09:00 AM IST/ 07:30 PM -09:30 PM CST
16 JAN
React with Redux (Online)
07:00 AM-08:30 AM IST
15 JAN
Big Data Hadoop Developer (Online)
05:00 PM to 06:30Pm IST / 06:30AM to 08:00AM CST
8 JAN
ASP.NET Core with Angular4 (Online)
09:00 Pm to 11:00 Pm IST (+5:30Gmt)
8 JAN
Big Data Hadoop Developer (Online)
07:00 AM - 08:30 AM IST(+5:30 GMT)
16 DEC
ASP.NET MVC with Angular4 (Classroom)
10:00 AM - 01::00 PM IST(+5:30 GMT)
12 DEC
ASP.NET MVC with Angular4 (Online)
09:00 PM - 11:00 PM IST(+5:30 GMT)
2 DEC
Developing Microsoft Azure Solutions (Online)
07:00 AM-09:00 AM IST / 08:30 PM Central Time
2 DEC
Angular2+4 with Firebase (Online)
10:30 AM-12:30 PM IST(+5.30 GMT)
27 NOV
ASP.NET Core (Online)
07:00 AM to 09:00 AM IST (+5:30 GMT)
11 NOV
ASP.NET MVC (Online)
08:00 AM-10:00 AM IST / 09:30 PM To 11:30 PM(CST)
SUBSCRIBE TO OUR YOUTUBE CHANNEL
 
 
 
LIKE US ON FACEBOOK
 
+