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 is function returns the same result if given the same arguments (it is also referred as deterministic) and does not cause any observable side effects
The code’s definitely easier to test. We don’t need to mock anything. So we can unit test pure functions with different contexts:
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.
if a function consistently yields the same result for the same input, it is referentially transparent.
Module in Node.js is a simple or complex functionality organized in single or multiple JavaScript files which can be reused throughout the Node.js application.Each module in Node.js has its own context, so it cannot interfere with other modules or pollute global scope.
require function is the easiest way to include modules that exist in separate files. The basic functionality of require is that it reads a JavaScript file, executes the file, and then proceeds to return the exports object
var module = require(‘module_name’);
As per above syntax, specify the module name in the require() function. The require() function will return an object, function, property or any other JavaScript type, depending on what the specified module returns
Use the exports keyword to make properties and methods available outside the module file