Introduction to Functional Programming

In Functional Programing, we want to express our whole program in terms of functions. Functional Programing is Declarative. This means we focus more on ** what to do ** instead of How to do

First, let's understand why Functional Programming is so important. Functional Programming enables us to

• Write re-usable code.
• Debug easily.
• Read better.

Functions are 1st Class Citizens because functions can be :

• Assigned to variables.
• Can be added to objects and arrays as well.
• Sent to other functions as an argument.
• Can be returned from other functions.

Let's get right into it.

** Non-Functional Way**

Functional Way

--> Pure Functions

A Pure Function is a function which, Given the same input, will always return the same output.

A Pure Function :

• Takes in at least 1 parameter.
• Return Something (A value or a function).
• Does not mutate any arguments.

Not Pure

The above code is not pure because

• --> It is not taking name as an parameter.
• --> It's dealing with something in the global scope.
• --> Also it not having a return value.

Pure Functions have no side effects which means it cannot alter anything outside the function.

Pure Function

Higher Order Function

A higher-order function is a function that takes a function as an argument, or returns a function or does both.

Immutable Code

Immutability means can't be changed.

Mutation --> (Bad)

Immutation

Last but not the Least Do not Iterate using for or while/loops --> Use Map, Reduce, Filter etc.

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