Data Types

Data types are how data in programming is classified. In JavaScript, there are eight fundamental data types:

Data Type Description
Number Any number, including numbers with decimals: 1, -2, 99, 3.14.
BigInt Any number, greater than 2^53-1 or less than -(2^53-1) with n appended to the number: 1234567890123456n.
String Any grouping of characters on your keyboard (letters, numbers, spaces, symbols, etc.) surrounded by single quotes '' or double quotes "".
Boolean This data type only has two possible values — either true or false.
Null This data type represents the intentional absence of a value, and is represented by the keyword null.
Undefined This data type is denoted by the keyword undefined. It also represents the absence of a value though it has a different use than null.
Symbol A newer feature to the language, symbols are unique identifiers, useful in more complex coding. No need to worry about these for now.
Object Collections of related data.

The first 7 of those types are considered primitive data types. They are the most basic data types in the language. Objects are a little more complex.

At first, eight types may not seem like that many, but they are the foundation that helps programmers build a whole new world.

Number and BigInt

var num = 7;
var bigNum = 9999999999999999n;

BigInt is necessary for big numbers because they are unreliable with Number type:



Strings in JavaScript can be defined with either ' ' or " ".

var greeting = 'Hi buddy';
var message = 'You are doing great! Keep studying!';


Boolean is for truthy or falsy values:

var lateToWork = true;
var isTheEarthFlat = false;

Null and Undefined

Null and Undefined are both for the absence of a value, but they have different meanings.

// Undefined means there should be some values, but it is undefined now
var finishCourseTime = undefined;
// Null means there is no value here
var finishStudyingDate = null;


Objects can have fields with different values and types inside:

const user = {
name: 'Jane',
age: 20,
isActive: true,


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