What is JavaScript Variable

In this article, we are reading about “What is JavaScript Variable“.
A JavaScript variable is simply a name of the storage location. There are two types of variables in JavaScript: local variable and global variable.
There are some rules while declaring a JavaScript variable (also known as identifiers).
  1. The name must start with a letter (a to z or A to Z), underscore( _ ), or dollar( $ ) sign.
  2. After the first letter, we can use digits (0 to 9), for example, value1.
  3. JavaScript variables are case sensitive, for example x and X are different variables.

A real-life analogy

We can easily grasp the concept of a “variable” if we imagine it as a “box” for data, with a uniquely-named sticker on it.
For instance, the variable message can be imagined as a box labeled “message” with the value “Hello!” in it:
What is JavaScript Variable
We can put any value into the box.
Also, we can change it. The value can be changed as many times as needed:
1
2
3
4
let message;
message = 'Hello!';
message = 'World!'; // value changed
alert(message);
When the value is changed, the old data is removed from the variable:
What is JavaScript Variable
We can also declare two variables and copy data from one into the other.
1
2
3
4
5
6
7
8
9
let hello = 'Hello world!';
let message;

// copy 'Hello world' from hello into message
message = hello;

// now two variables hold the same data
alert(hello); // Hello world!
alert(message); // Hello world!

Correct JavaScript variables

1
2
var x = 10;
var _value="sonoo";

Incorrect JavaScript variables

1
2
var 123=30;
var *aa=320;

Example of JavaScript variable

Let’s see a simple example of JavaScript variable.
1
2
3
4
5
6
<script>
var x = 10;
var y = 20;
var z=x+y;
document.write(z);
</script>
Output
1
30

JavaScript local variable

A JavaScript local variable is declared inside block or function. It is accessible within the function or block only. For example:
1
2
3
4
5
6
7
8
9
10
11
<script>
function abc(){
var x=10;//local variable
}
</script>
Or,
<script>
If(10<13){
var y=20;//JavaScript local variable
}
</script>

JavaScript global variable

A JavaScript global variable is accessible from any function. A variable i.e. declared outside the function or declared with window object is known as global variable. For example:
1
2
3
4
5
6
7
8
9
10
11
<script>
var data=200;//gloabal variable
function a(){
document.writeln(data);
}
function b(){
document.writeln(data);
}
a();//calling JavaScript function
b();
</script>
Output
1
200 200
So in this article, we read about “What is JavaScript Variable“.

Comments

Post a Comment

Popular posts from this blog

Java Number Class

Image
In this article we are reading about  “ Java Number Class ” . Java Number class is an  abstract  class which is placed in  java.lang  package. It has  four  abstract methods and two  concrete methods. The abstract class Number is the superclass of classes BigDecimal, BigInteger, Byte, Double, Float, Integer, Long, and Short. This class contains a single consructor  number() . In Java language, we mostly work with a  primitive data type , but Java also provides a  wrapper class  under the abstract class numbers in java.lang package, there are six subclasses under the class ‘numbers’. The primitive data types are ‘wrapped’ under these Java classes for their corresponding objects. This wrapping is usually done by the compiler. When an object is converted into primitive type than it is called Autoboxing, and then again transferred to an object it is called Unboxing. The following figure shows the class hier...
Read more

Java Character Class

In this article we are reading about  “ Java Character Class ” . The Character class simply a wrapper class for the primitive type char. It wraps the char primitive value to an object. An object of type Character contains a single field whose type is char .  So what would be the benefit if wraps around the primitive data type to an object? Well basically we would be able to access all the methods that is readily available on the Character class which is very useful. In addition, this class provides several methods for determining a character’s category (lowercase letter, digit, etc.) and for converting characters from uppercase to lowercase and vice versa. We will go over each and every method available to Byte class thoroughly. Character information is based on the Unicode Standard, version 6.2.0. The methods and data of class Character are defined by the information in the UnicodeData file that is part of the Unicode Character Datab...
Read more

What are Web Resources in Microsoft Dynamics 365?

Image
In this article we are reading about  “What are Web Resources in Microsoft Dynamics 365 ?” . Web Resources in Dynamics 365  are virtual files stored in the Dynamics 365 Database and typically used by developer and designer to extend web application. In Dynamics 365(online), we use Web resources to upload upload files to Dynamics 365 database and then reference them by name. In Dynamics 365, Web resources are limited to specific types of filters. The following types of files can be used to create Web Resources in Dynamics 365. File Type File name extension Webpage (HTML) .htm, .html Style Sheet(CSS) .css Script(Jscript, JavaScript) .js Data (XML) .xml Image (PNG, JPG, GIF) .png, .jpg,  .gif. Silverlight (XAP) .xap StyleSheet(XSL) .xsl, .xslt Image (ICO) .ico How to create Web Resource in Dynamics 365? To create Web Resource in Dynamics 365, navigate toSettings | Customizations | Customize the System. Now go toComponents | Web Resources | Click...
Read more