What is functional programming

• Functional programming is a programming paradigm — a style of building the structure and elements of computer programs — that treats computation as the evaluation of mathematical functions and avoids changing-state and mutable data

Pure functions

• It returns the same result if given the same arguments
  • ` let PI = 3.14; ` ` const calculateArea = (radius) => radius * radius * PI; ` ` calculateArea(10); // returns 314.0 `
• It does not cause any observable side effects
  • let counter = 1; function increaseCounter(value) { counter = value + 1;} increaseCounter(counter); console.log(counter); // 2

_ pure functions:

• It returns the same result if given the same arguments.

• It does not cause any observable side effects.

• EX: impure function:
  • let PI = 3.14;
  • const calculateArea = (radius) => radius * radius * PI;
  • calculateArea(10); // returns 314.0
• Immutability:
• Unchanging over time or unable to be changed.
• When data is immutable, its state cannot change after it’s created.
• If you want to change an immutable object, you can’t.
• Instead, you create a new object with the new value.

Referential transparency

• Basically, if a function consistently yields the same result for the same input, it is referentially transparent.
  • ` pure functions + immutable data = referential transparency `

Standards

• There is no doubt that standards help to improve the quality of code. It’s important to check for those standards while refactoring your code