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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

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