JavaScript Data Types

Data types define the type of data a variable can hold. In JavaScript, different data types are used to store numbers, text, true/false values, and more.

JavaScript is a dynamic language, which means you do not need to declare the type of a variable. The type is automatically determined.

Types of Data in JavaScript

JavaScript has several built-in data types. The most common ones are:

String
Number
Boolean
Undefined
Null

String

A string is used to store text. It can be written inside single or double quotes.

Example

<!DOCTYPE html>
<html>
<body>    
 <p id="str"></p>

<script>
let name = 'John';
document.getElementById('str').innerHTML = name;
</script>

</body> 
</html>

Try this code

Number

Numbers are used to store numeric values such as integers and decimals.

Example

<!DOCTYPE html>
<html>
<body>    
<p id="num"></p>

<script>
let x = 10;
let y = 5;
document.getElementById('num').innerHTML = x + y;
</script>

</body>
</html>

Try this code

Boolean

A boolean data type can have only two values: true or false.

Example

<!DOCTYPE html>
<html>
<body>
<p id="bool"></p>

<script>
let isOnline = true;
document.getElementById('bool').innerHTML = isOnline;
</script>

</body>
</html>

Try this code

Undefined

A variable that is declared but not assigned a value has the type undefined.

Example

<!DOCTYPE html>
<html>
<body>      
<p id="undef"></p>

<script>
let x;
document.getElementById('undef').innerHTML = x;
</script>

</body>
</html>

Try this code

Null

Null represents an empty value. It is intentionally assigned to a variable.

Example

<!DOCTYPE html>
<html>
<body>      
<p id="null"></p>

<script>
let data = null;
document.getElementById('null').innerHTML = data;
</script>
</body>
</html>

Try this code

The typeof Operator

The typeof operator is used to check the data type of a variable.

Example

<!DOCTYPE html>
<html>
<body>      
<p id="type"></p>

<script>
let x = 'Hello';
document.getElementById('type').innerHTML = typeof x;
</script>
</body>
</html>

Try this code

Why Data Types are Important

They help in storing different kinds of data
They make code easier to understand
They prevent errors in programs
They are essential for logical operations