# Datatypes in JavaScript?

# What are Datatypes in a programming language?

Datatypes define the type of data the variable can store. Based on these datatypes a variable can perform certain operations which other datatypes might not perform.

Examples of datatypes: String, integer, Boolean, etc.

# How do you declare a variable with a certain datatype in JavaScript?

Since JavaScript is a dynamically-typed language so you cannot specifically declare the type of the variable.

***Dynamically-typed languages are those (like JavaScript) where the interpreter assigns variables a type at runtime based on the variable's value at the time.***

So you just declare a variable with let or const or var and based on the value of that variable JavaScript will automatically assign the type to the variable.

# Datatypes in JavaScript?

The following datatypes are present in JavaScript:

1\. String- stores a string value. You add value inside either double quotes or single quotes or backtick(backtick is present below Esc button).

```javascript
let s="string data type stores string value,in double quotes";
let s1='string data type stores string value,in single quotes';
let s2=`string data type stores string value,in backticks`;
```

1. Number- stores integer value.
    
    ```javascript
    let x=20;
    ```
    
2. Boolean- stores either true value or false value. Generally used for checking a condition.
    
    ```javascript
    let bool=true;
    let bool2=false;
    ```
    
3. Undefined- In JavaScript, a variable without a value, has the value undefined. The type is also undefined. Any variable can be emptied, by setting the value to undefined. The type will also be undefined.
    
    **<mark>Don't confuse an empty string with an undefined, both are different. An empty string is still a string.</mark>**
    
    ```javascript
    let car;//stores undefined 
    let car1 = "Volvo";
    car1 = undefined;//previously car1 was storing a string, now it is empty;
    ```
    
4. Array- it is a collection. It can be a collection of strings, numbers, or both, or can be a collection of array itself. Generally, arrays will be meaningful collections like collections of phoneNumbers etc.
    
    JavaScript arrays are written with square brackets.
    
    Array items are separated by commas.
    
    ```javascript
    let countries=["India","USA","Russia"];
    let mix=["India",1,true];//contains a string, a number, a boolean value
    ```
    

There are other datatypes as well like Bigint, Null, Symbol, and Object, the most common ones that are widely used except for Object are explained.<mark>Object is a new topic in itself and very important, will be covered in upcoming blogs.</mark>

***<mark>Note: The datatype of a variable can switch from string to number, from number to boolean and so on, in JavaScript.</mark>***

```javascript
let x=10;//here the type of x is number
x="India";// but here it became a sting.
```

## The typeof Operator

You can use the JavaScript `typeof` operator to find the type of a JavaScript variable.

The `typeof` operator returns the type of a variable or an expression.

```javascript
x=10;
console.log(typeof x);//returns Number
```

***<mark>Thank you for reading. Have a nice day ahead.</mark>***