Javascript Variable

Michael Zippo 04.11.2021

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Variables are an integral part of almost all programming languages ‚Äã‚Äãand are usually one of the first things you learn when you start programming. Variables can be used to store data in a program, such as strings, numbers, JSON objects, or Boolean values.

In JavaScript, there are three types of variables:. var, let and const. Each of these variables has different rules for how they should be used and has different characteristics.

In this tutorial, we will explore the basics of variables in JavaScript. We will discuss how to name a JavaScript variable, when you need to use the var, let, and const variables and explore how to raise and the variables impact dell. " field.

JavaScript variables

Variables are used to store data values. For example, a variable can be used to store a user’s email address or name. In JavaScript, a variable can contain any type of data, such as a string, a true or false Boolean, an object or a number.

Before the ES6 specification was released, there was a way to declare a JavaScript variable: var. var keyword can be used to declare a variable accessible in a program and can be changed.

Here is an example of a variable declared using var in JavaScript:

Our variable can be divided into a few components:

var is used to declare our variable
full_name is the name of our variable
= tells our program that we want to assign a value to our variable (we call this operator assignment)
Alexander Smith is the value of our variable will remember

Now that we have demonstrated the creation of a JavaScript variable, we can the use in our code. Here is an example of a JavaScript program that uses our variable:

Our code returns:

To declare a variable which has no value, you can use the code var variableName , but without assignment. Here is an example of a variable declared without value:

So if we want to assign a value to our variable we can use this code:

optional, we can add var at the start of our task, like this:

Now if we print ourExampleVariable the console, we get the following response: Example

Our variable can store any type of data, as we discussed earlier. Here is an example of some variables that have been assigned different data types:

How to Name JavaScript Variables

Every programming language has its own rules for how to name variables, and JavaScript is no different. Here are the main rules to consider when naming variables in JavaScript:

, JavaScript also uses case sensitive to declare variable names . This refers to writing the first word of a variable in lowercase, then capitalizing each future word in the variable. Here is an example of a variable declared in camel case:

If we have only one word in our variable, each letter must be lowercase.

Also, if you declare a variable using const, each letter must be in upper case.

While this is a lot of information to learn, over time you will naturally be able to figure out what your variables should be named. All you have to do is practice!

Var, Let and Const Variables

There are three different keywords for declaring a JavaScript variable. They are: var, let and const

Here is a table that breaks down the differences between these three types. variables:

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Word	variable scope	Reassign?	redeclare?	Raise?
var	Function	Yes	Yes	Yes
const	Block	Yes	No	No
quit	Block	No	No	No

The following are general rules for using these types of variables:

Use const , whenever possible, unless you need to replace or increase a variable .
Use let if you are working with loop .
Use only var if:

You are working on previous code ,
You need a variable that you can re-claim or
you need a variable that is accessible anywhere in the program (globally) .

If you are interested in learning more about these types of variables, check out our tutorial on how to use JavaScript let variables here

This table contains a lot of information, so we’ll analyze each of the main differences between these types of variables: . field, reassignment, rideclaration and hissage.

Scope
Scope is used to designate where a variable is accessible within a program. There are two application fields in JavaScript: global scope, which is where a variable is declared outside of a block of code; and local goal, where a variable is declared in a code block

Here is an example of a global variable in JavaScript:

This variable is available throughout our program. So if we want to access our name variable later in functions, we can do that.

Local variables are declared in a given code block. To declare a local variable, you must use let and const, which are assigned a block field. Here is an example of let used in a program:

Our code returns the elements include:

As you can see, since day is the same as Monday, our program runs the contents of our if declaration. Then our program changes the value of the flavor variable Choc-Chip and prints the first message we saw above.

But after if the declaration was executed, the value of flavor returns to Vanilla, which was declared globally at the start of our program. Then, in the last line of code, our program prints a message asking us to have a scoop of vanilla ice cream, because flavor has been assigned the value Vanilla in the world.

redeclaring Variables
In JavaScript, only var variables can be redeclared. This means that you can create a new variable with the same name and keep its value, or assign a different value to the variable.

Here is an example of a program that declares a variable called RADIOSHOW, redeclares the variable:

Our code returns: KACL. In our code, we declared RADIOSHOW twice. Without useful in the previous example, if we had an older program, we might want to redeclare a variable. Therefore, if we expect to want to redeclare a variable, we should use var to declare it.