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What are JavaScript Data Types? | A Beginner's Guide


No matter whether you are a mediocre level or experienced developer, you will get the solutions to your problems coming during the development jobs. has started writing tutorial blog posts in the programming category and we are starting with a JavaScript beginner’s guide. Since we are starting off so this article is about JavaScript data types. Let’s explore what are JavaScript data types and see examples of how can you use them in the source code efficiently. Therefore, go through this beginner’s guide thoroughly so you can have a good understanding of JavaScript data types.

We are covering the following point:

Data Types Explained | What is a data type?

A data type is all about telling the compiler how to interpret or compile the data. The usage of data types is critical and must be used wisely. In simple words, it is about the format of the data such as Number, String, Boolean and more. However, there are two categories of data types Primitive data types and Non-Primitive data types. There are eight Primitive data types that we will go through in the next section.

What are JavaScript Data Types?

In fact, JavaScript is a loosely typed language which means you do not have to define the variable type explicitly. You can assign any value to a variable and that variable will store that value such as String, BigInt, Boolean, or more.

JavaScript beginner's guide

Primitive Data Types

Primitive data types are those which are immutable and cannot be changed after the creation and initialization. However, you can re-assign a new value but cannot mutate the existing value.

For example:

var name = "my name is mustafa";
name = "my name is changed";
console.log(name) // output:  my name is changed
name[0] = "M";
console.log(name) // output: my name is changed

In the example above, String is a primitive data type and the old value is being replaced by the new value but the change in the existing value is not being reflected. So, we can see it is still “my name is changed” not “My name is changed”;

Non-Primitive Data Types

Non-Primitive data types are mutable, in simple words opposite of primitive data types.

For example:

var arr = [1,2,3];
arr[0] = 11;
console.log(arr) // output: [11,2,3]

In addition, primitive data types are compared by value, and non-primitive data types are always compared by reference.

For example:

// Primitive Data Type

var first_name = "mustafa";
var last_name = "mustafa";
first_name === last_name  // true

// Non-Primitive Data Type

var arr = [1,2];
var arr2 = [1,2];
arr === arr2 // false
// BUT
var arr = [1,2];
var arr2 = [1,2];
arr = arr2;
arr === arr2 // true

Now, let’s go through the data types one by one. There are 6 primitive data types and 1 non-primitive data type.

Primitive Data Types include:

  • String: This data type represents textual data which consists of a sequence of characters surrounded by quotes.
  • Number: It represents decimal/non-decimal data, particularly integer or float.
  • Boolean: Representation of logical values true or false.
  • Symbol: Symbol is used to hold unique values.
  • Undefined: A variable without any value or an uninitialized variable.
  • Null: The absence of any value is considered Null.

Non-Primitive Data Type includes:

Object: It is used to store the collection of data consisting of key-value pairs.


This is the end of this JavaScript beginner’s guide. We have gone through what are JavaScript Data Types? In addition, we have explored what is a Data Type in a nutshell. You should have a better understanding of Non-Primitive and Primitive Data Types in JavaScript. This blog post will really help you if you are looking to do preparation for a job interview.

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What are the 8 JavaScript data types?

Please visit this link to know the 8 JavaScript Data Types.

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