# JavaScript Variables

# **What is JavaScript Variable?**

Variables means anything that can vary and holds the data value and we can mutate it anytime. A variable must have a unique name. Javascript includes variables that hold the data value and it can be changed on runtime as javascript is dynamic language. We have **var, const,** and **let** keyword to declare a variables.

**Example:**


```
const name='vignesh'
let age=25;
var city='bengaluru'

console.log(name) //vignesh
console.log(age) //25
console.log(city)//bengaluru
``` 

# **Rules for Naming Variables**

- The first character must be a letter or an underscore (_). We can't use a number as the first character.

- The rest of the variable name can include any letter, any number, or the underscore. We can't use any 
   other characters, including spaces, symbols, and punctuation marks.

- JavaScript variables are case sensitive, for example aa, AA and aA are different variables.

###  **Types of variables in JavaScript :**

- **Local Variable**

local variables are only visible in the function in which we define them. They will not have any significance outside that function.

**Example:**

```
function details()
{
  const name='vignesh'; //local var
  let ages=25;          //local var
  console.log(`Name: ${name} age:${ages}`);//Name: vignesh age:25 
}

details();
``` 


- **Global variable**

Global variables have global scope i.e. they can be defined anywhere in your JavaScript code.

**Example:**


```
const name='vignesh';    //Global var
let ages=25;         //Global var

function details()
{
    console.log(`Name: ${name} age:${ages}`);   //Name: vignesh age:25 
}
console.log(`Name: ${name} age:${ages}`);      //Name: vignesh age:25 
details();

```