Data Types in JavaScript

What is a Data Type?

In JavaScript, everything is data except:

Operators: +, !, <=, etc…

Reserved words: functions, for, debugger, etc.

In JavaScript, every kind of data falls into JavaScript’s seven data types which include numbers, strings, booleans, symbols, objects, null and undefined

How to identify a data type?

One way to find out what type of data type we are dealing with is typeof operator.

See below:

Numbers —

In Javascript, we have a single one encompassing number type, in other languages divide the numbers into integers, decimals, doubles and floats to have higher precision.

Using typeof operator on numbers
NOTE*Keep in mind that as JavaScript has become a language for the backend and front end, because of its imprecision for numbers, keeps it from development in banking or engineering applications where precision is vital.

Strings —

Strings are used to represent text in JavaScript. Strings are represented by using 'single-quotes', "double-quotes", `backticks` with zero or more characters inside.

Using typeof operator on strings

Booleans —

Boolean returns of two possible values: true or false. Booleans are important and play a big role in if statements in JavaScript.

Using typeof operator on booleans

Objects —

In JavaScript, objects are a collection of properties in curly braces {}. The properties point to values of any data type — they can even be objects. Example below:

Using typeof operator on objects

null and undefined —

The null data type falls under an intentionally absent object. Undefined usually means that something has not yet been assigned a value


Knowing your data types is important because if you're aware of what data type you're working with makes it easier to determine what values you can assign to it and what can you do with the data type.

MDN — JavaScript data types and data structures

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