Javascript closures and side effects in plain English? (separately)

Question

I\'ve been reading some JavaScript books and I always hear about closures and side effects. For some reason I can\'t understand what they really are. Can anyone explain to m

Answer 1

Mainly side effects are the interactions with the outside world from inside of the function. Some examples of the side effects are:- API Calls or HTTP requests, data mutations, Printing to a screen or console, DOM Query/Manipulation. Example :

var a = 12
function addTwo(){
   a = a + 2; // side-effect

}
addTwo()

Closures

According to MDN,

A closure gives you access to an outer function’s scope from an inner function. In JavaScript, closures are created every time a function is created, at function creation time.

Example :

function outer(){
  var a = 12; // Declared in outer function 
  function addTwo(){ // closure function
    a = a + 2; // acessing outer function property
    console.log(a)
  }
  addTwo();
 }
 outer()