# JavaScript-Variables

# Let's understand what really variables in JS-

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1672338952636/249713b8-320e-47e9-bf70-918aeee065d4.gif align="center")

*Here are some definitions-*

Variables are containers that hold reusable data. It is the basic unit of storage in the program. OR

A value stored in a variable can be changed during program execution. A variable is only a name given to a memory location, all the operations done on the the variable effects that memory location.

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1672339822862/5e60cbb7-9609-4157-86f7-3de6117b94a3.png align="center")

Note: Before 2015- Variables declared using var keyword followed by the name of the variable name and semicolon.

```javascript
var number = 37;
```

## Imp....

```javascript
let full_Name = 'Anurag Tiwari';
```

The full\_Name is the name of the variable which should be defined by the user and should be unique that match your task. These types of names are also known as identifiers.

In Javascript, the name of the identifiers should not be any pre-defined word, the first character must be a letter , an (\_) or a ($) sign.

Storing a mathematical exp-

```javascript
var x = 3 + 34 + 3;
console.log(x) ;
```

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1672340629525/2f2648e0-d907-4737-b706-e6ed40395cc8.gif align="center")