JavaScript Data Types

Beginner ~12 min read

Dynamic Typing

JavaScript is a dynamically typed language. This means you don't have to specify the data type of a variable when you declare it, and data types are converted automatically as needed during script execution.

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<h2>Dynamic Typing Demo</h2>
<p id='output'></p>

Primitive Data Types

JavaScript has 7 primitive data types:

String: Text data, e.g., "Hello"
Number: Integer or floating-point, e.g., 42, 3.14
BigInt: Integers with arbitrary precision
Boolean: true or false
Undefined: A variable that has not been assigned a value
Null: Intentional absence of any object value
Symbol: Unique and immutable primitive

The `typeof` Operator

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

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<h2>Typeof Demo</h2>
<p id='types'></p>

Objects

Objects are collections of key-value pairs. They are the most important data type in JavaScript.

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<h2>Object Demo</h2>
<p id='person'></p>

Arrays

Arrays are a special type of object used to store multiple values in a single variable.

const cars = ["Saab", "Volvo", "BMW"];

Summary

JavaScript variables can hold many data types: numbers, strings, objects and more.
JavaScript has dynamic types.
Strings are written with quotes.
Numbers are written with or without decimals.
Booleans can only have two values: true or false.

Quick Quiz

What is the data type of the value 'Hello'?

Number

Boolean

String

Object

Previous Variables

Next Operators

Dynamic Typing

Primitive Data Types

The typeof Operator

Objects

Arrays

Summary

Quick Quiz

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The `typeof` Operator