JavaScript Variables

by | Jan 25, 2023 | CentOS 7, JavaScript, Linux Basics, Linux Server, Virtualization, VPS Servers

JavaScript Variables

JavaScript Variables

For any programming language has a fundamental requirement to store data in memory such that computations can be performed on it.

And the memory location requires a name to store and retrieve this data, and this name is “Variable.”

Basically, only one type of data can be stored in each memory location. IF you want then buy a good, reliable, secure web hosting service  from here: click here

Also, the variable “DataType” helps to determine this each programming language permits the definition and declaration of variables of particular data types because it must perform some computation, and JavaScript is no exception.

What are JavaScript Variables?

Firstly, anything that can change is considered to be a variable and a variable in JavaScript saves data that can be modified later.

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Secondly, the variable is uniquely identified by its name,

Thirdly, the value pertains to the information kept in the variable, and

Fourthly, the variable’s memory location is indicated by the memory address.

How to Declare a Variable in JavaScript?

In JavaScript, defining a variable is referred to as “Declaring” a variable, and additionally, the “var” keyword is utilized to declare the variable.

So, the JavaScript keywords var, let, and const can be used to declare the variables described below:

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Var: the var keyword has been used to declare variables since JavaScript was developed. So, it is unclear and prone to error when variables are declared using var.

Let: In JavaScript let keyword gets rid of var’s ambiguity and error. The new and advised method of declaring variables for JavaScript.

Const: In JavaScript, a constant variable is one that is given a value, cannot be modified, and is declared with the const keyword.

Rules for Establishing JavaScript Variables

A few of these laws include are below:

First: The first character of a variable name must be a letter, an underscore (_), or a dollar symbol ($).

Second: You can use numbers after the initial letter, underline, or dollar.

Third: Spaces are not permitted in variable names.

Fourth: JavaScript class variables are case-sensitive.

Fifth: Reserved words, such as abstract, final, etc., cannot be used as variable names.

Sixth: The script> tag allows JavaScript code to be included in an HTML document.

// Valid variables
var test1 = 10; // Started with letter
var  _test = “Demo”; // Started with UnderScore(_)
var $test1 = true; // Started with dollar sign($)

// Invalid variables
var 1test = 10; // Started with letter 1
var *test = “value”; // Started with special character(*)

What Is the Scope of JavaScript Variables?

Local Scope: JavaScript environment variables fall under the local scope when they are declared inside a function, method, or block. So, in this methods/functions are the only places where these variables can be accessed.

<html>
<head>

      <script type = "text/JavaScript">
            function checkVariable( ) {
               // local variable just accessed in this feature
               myVar = "ToolsQA";
              document.write(myVar);
         }
   </script>

</head>

<body onload = checkVariable()>
</body>

</html>

Now, consider the following scenario when a user wants to access a local variable specified in one method from another method like the below:

<html>
<head>
<script type="text/JavaScript">
function checkVariable( ) {
// local variable declaration and setup
var myVar = "ToolsQA";
}

function clickButton(){
// try accessing local variable in another method
alert(myVar);
}
</script>
</head>

<body onload=checkVariable()>
<button onclick="clickButton()">Click me</button>

</body>
</html>

Global Scope: In JavaScript, variables declared outside of all the functions or methods are referred to as global variables and are accessible to all methods, functions, and blocks. For instance, in the code excerpt like below:

<html>
<head>
<script type="text/JavaScript">
//this is the global variable, and it can be accessed in all the functions
var myVar;
function checkVariable( ) {
// Assign value to the global variable
myVar = "ToolsQA";
}

function clickButton(){
// Print value of the global variable
alert(myVar);
}
</script>
</head>

<body onload=checkVariable()>
<button onclick="clickButton()">Click me</button>

</body>
</html>

Conclusion

Lastly, a JavaScript variable is the name of a storage location. It is a label for a value, such as a string or a number.

However, we need to must declare a variable before using it. Now we know that the basics of JavaScript variables, don’t be afraid to use them in our projects.

That’s it. If you enjoyed reading this article and have more questions please reach out to our support team via live chat or email and we would be glad to help you. we provide server hosting for all types of need and we can even get your server up and running with the service of your choice.