# Variables in JavaScript

what is variable?

The word **variable** means that can vary. variable is a container for storing data Javascript variable can store any data values (e.g., a number, a string,a boolean,etc)


![Screenshot 2022-09-10 141300.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1662799411227/iWHXpEQEn.png align="left")

How variable is created?

variable is created using  var, let, const keywords

![Screenshot 2022-09-10 141704.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1662799654539/pW2ytBvaL.png align="left")

Difference Between var ,let,const?

when to use which keyword for a variable 

![differencebetweenvariablekeywords.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1662800461968/McjGceNZZ.png align="left")

**Var**

when we write looping code like this


![vareample.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1662801935945/qu-k4juOO.png align="left")

![varkeyword.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1662800801882/YrNWf7-AL.png align="left")

The end of the code will show “after loop 5”. Even though i variable just declare in looping for. This happen is because in JavaScript, syntax var runs on the function scope. Which means that variable we declare in a function as long as they are still in the scope of the function.


**let**

To find out about the let syntax, I will make a loop code like in the first case. However, in this code I will use the let i syntax.


![let.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1662801231863/PIv5Cd5JL.png align="left")

Unlike the var syntax, if the code is executed it will produce an error in the form of “ReferenceError: i is not defined” which indicates that the variable i has not been declared. Even though I declared the variable i in the loop for. This is because the let syntax is a block scope.

**Const**

Const has the same properties as let only, if we declare a variable with const syntax, we cannot reassign the value of that variable.

![const.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1662801595633/02gXo-dNL.png align="left")

In the first condition (using the let syntax), the final result of variable i is 2.
Whereas in the second condition (using the const syntax), it will produce error “TypeError: Assignment to constant variable.” which indicates that variable i cannot be reassigned.

**conclusion**

The var syntax shows that variables declared with var syntax can be reassigned and can be used in the function scope.

The let syntax indicates redeclaring a variable in the same block is NOT allowed and can only be accessed in a block scope.

The  variables declared with the const cannot be reassigned.