Variables In JavaScript

Introduction

 
In this article we will cover the basic concepts of JavaScript, the most important being variables and data types.
 

Variable

 
A Variable is an identifier or a name that is used to refer to a value. It is media to store the information to be referenced and manipulated in a computer program. Using the key of a variable in JavaScript “var”, the extension is important (.js).
 
Syntax
  1. var <variable-name>;      
  2. var <variable-name> = <value>;    
Note
 
In the example, the number 10 is assigned to “a”. Use only the special characters  (__) underscore and ($) symbol, don't use other special characters like @, *, %, #. JavaScript is case sensitive.
 
In this example the variable name ‘a’ is uppercase,
  1. var a=10;  
  2. document. Write(A);  //varible name is lowercase
Error - ‘a’ is not found
 
Example 1
  1. <!DOCTYPE html>  
  2. <html>  
  3. <head>  
  4.     <title>Java Script</title>  
  5. </head>  
  6. <body>  
  7.     <h4>Variables in JavaScript</h4>  
  8.     <script>  
  9.         var a = "30";  
  10.         document.write(a);  
  11.     </script>  
  12. </body>  
  13. </html>
Output
 
 
Example 2
  1. <!DOCTYPE html>  
  2. <html>  
  3. <head>  
  4.     <title>Java Script</title>  
  5. </head>  
  6. <body>  
  7.     <h4>Variables in JavaScript</h4>  
  8.     <script>  
  9.         var name = "vijay";  
  10.         document.write(name);  
  11.     </script>  
  12. </body>  
  13. </html> 
Output
 
 
There are two types of Variables
  • Local Variable
  • Global Variable

JavaScript Local Variable

 
The local variable is a variable in which a variable can be declared within the function, and it can be used only inside that function. So, variables with the same name can be used in different functions.
 
Example
 
//local Variable
  1. <!DOCTYPE html>  
  2. <html>  
  3. <head>  
  4.     <title>Java Script</title>  
  5. </head>  
  6. <body>  
  7.     <h4>JavaScript</h4>  
  8.     <script>  // local variable
     
  9.         function article (){  
  10.         var name = "Variables in JavaScript";  //inside the function declare a variable
     
  11.         document.write(name);  
  12.     }  
  13.     article();  
  14. </script>  
  15. </body>  
  16. </html> 
Output
 
 

Global Variable

 
The global variable is a variable in which variables can be defined outside the function. So, variables with the same name cannot be used in different functions.
 
Example
 
//Global Variable
  1. <!DOCTYPE html>  
  2. <html>  
  3. <head>  
  4.     <title>Java Script</title>  
  5. </head>  
  6. <body>  
  7.     <h4>JavaScript</h4>  
  8.     <script>  //global variable
     
  9.         var articlename = "variables in JavaScript";  //outside the function declare a variable
     
  10.         function article ()   
  11.         {  
  12.         document.write(articlename);  
  13.         }  
  14.         article();  
  15. </script>  
  16. </body>  
  17. </html> 
Output
 
 

Summary

 
In this article, we looked at how to declare a variable in JavaScript. In my next article, we will learn what the data types in JavaScript are. I hope this article is very useful for you.
 
Thanks for reading.