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Chaoo Charles
Chaoo Charles

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JavaScript happens to be one of the most popular programming language in 2021. One of the reasons is because it's the only programming language used on the front-end web development. If you are looking forward to be a web dev, then JavaScript is very important to understand. One of the core concepts is JavaScript is Data Types. In this blog post we will cover data types in depth.

JavaScript is Dynamically typed

πŸ”Ή A value in JavaScript is of a certain type.
πŸ”Ή Types in JavaScript are not bound to variables.
πŸ”Ή This means that you don't specify the types when declaring a variable.
πŸ”Ή JavaScript is therefore said to be a Dynamically typed programming language.
πŸ”Ή You will also find some blog posts calling it loosely typed. It means the same thing.

  • See below ⬇

loosely typed

JavaScript has 8 data types.

The 7 primitive data types:
πŸ”Ή Boolean
πŸ”Ή null
πŸ”Ή undefined
πŸ”Ή Number
πŸ”Ή BigInt
πŸ”Ή String
πŸ”Ή Symbol

The non-primitive data type:
πŸ”Ή Object

  • Note that arrays and functions are objects.
  • Functions are special objects with a function value.
  • See below ⬇

arrays and functions are objects

Difference between primitive types and non-primitive types

πŸ”Ή Primitives have immutable values (cannot be changed)
πŸ”Ή non-primitive have mutable values (can be changed)

  • Don't confuse changing a value with changing a variable
  • Variables are not values
  • See below ⬇


πŸ”Ή Primitives are compared by value. The same values are strictly equal. They exist at the same memory location.
πŸ”Ή non-primitive are not compared by value. Two objects with the same properties and values are not equal. They are created at different memory locations.

  • See below ⬇


Let's go through the primitive types

1/7 Boolean

πŸ”Ή A Boolean type has only two values, true and false.

  • They are mostly used for comparisons.
  • See below ⬇


2/7 null

πŸ”Ή A null type contains only the null value.
πŸ”Ή A null value means nothing, empty or unknown value.

  • Note that there is an error in JavaScript. null pretends to be an object. It is NOT an object. It is a primitive type. -See below ⬇


3/7 undefined

πŸ”Ή The undefined type contains only the undefined value.

  • If a variable is declared but not assigned, then its value is undefined.
  • Not that undefined is not similar to not defined.
  • See below ⬇


4/7 Number
πŸ”Ή Number type includes integers, floating point numbers, infinity, -infinity, -0, and NaN.
πŸ”Ή You can do Mathematical operations e.g +, -, e.t.c

  • NaN means Not a Number. -See below ⬇


5/7 BigInt
πŸ”Ή This type is used to represent very large integers.

  • Use cases include cryptography and financial calculation where precision is important.
  • You will rarely use it.
  • See below ⬇


6/7 String
πŸ”Ή A string type represents text in JavaScript

  • They must be surrounded by quotes or backticks.
  • See below ⬇


7/7 Symbol
πŸ”Ή The symbol type is used to create unique identifiers for objects.

  • It's hard to explain them without diving deeper into objects and properties. So, we are going to skip them for now.

That's it for today. I hope you learned something. We will cover objects, arrays, and functions on their own separate blog posts.

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