closure.js

function largestOfFour(arr) {
  let maxOfArray = [];
  return function iterator(arr){
   for (var i = 0; i < arr.length; i++)
        if (Array.isArray(arr[i])){
            console.log(arr[i]);
            iterator(arr[i])
        }
        else{
            console.log(arr[i])
        }
  }      
}

largestOfFour()([[4, 5, 1, 3], [13, 27, 18, 26], [32, 35, 37, 39], [1000, 1001, 857, 1]]);

console.log('--------------------------------');

const array = [1,2,3,4];
for(var i = 0; i < array.length; i++){
    (function(closureI){
        setTimeout(function(){
            console.log("I am at index " + array[closureI])
        },1000)
    })(i)
}

console.log('--------------------------------');

function count(){
    let changedArray = [];
    return function(array){
        for(var i = 0; i < array.length; i++){
            changedArray.push(i);
            console.log(changedArray);
    setTimeout(function(){
        console.log("I am at index " + changedArray[0])
         changedArray.shift();
    }, 1000)
}
    }
}

const counting = count();
counting([1,2,3,4]);


console.log('--------------------------------');


function initialize(){
    let isInitialized = false;
    let view;
       return function setView(){
         if(isInitialized){
        return undefined;
        }
        else
        {
        isInitialized = true;
        return view = "perfect image";
        }
    }
   
}

const startOnce = initialize();
startOnce()

console.log('--------------------------------');

const makeNuclearButton = () => {
let timeWithoutDestruction = 0;
const passTime = () => timeWithoutDestruction++;
const totalPeaceTime = () => timeWithoutDestruction;
const launch = () => {
timeWithoutDestruction = -1;
return '💥';
}
setInterval(passTime, 1000);
return {totalPeaceTime}
}
const ww3 = makeNuclearButton();
ww3.totalPeaceTime() // example of encapsulation

console.log('--------------------------------');

var increment = (function(n) {
  return function() {
    n += 1;
    return n;
  }
}(0)); // -1 if you want the first increment to return 0

console.log('--------------------------------');

var increment = function() {
    var i = 0;
    return function() { return i += 1; };
};

var ob = increment();

console.log('--------------------------------');

function greet(whattosay) {
  return function(name) {
    console.log(whattosay + ' ' + name);
  }
}

greet('Hi')('Tri');
var sayHi = greet('Hi');
sayHi('Tri');

console.log('--------------------------------');

// A classic example of closure

function buildFunctions() {
  var arr = [];
  for (var i = 0; i < 3; i++) {
    arr.push(
      function () {
        console.log(i); // draw out the call stack, you will see how all three
                        // call to console.log(i) will point to the same i
                        // which last value is 3
      }
    )
  }

  return arr;
}

var fs = buildFunctions();

fs[0]();
fs[1]();
fs[2]();

console.log('---------------');

function buildFunctions2() {
  var arr = [];
  for (var i = 0; i < 3; i++) {
    let j = i;
    arr.push(
      (function(j) {
        return function() {console.log(j);}
      })(i) // Using immediate invoke function expression to create a new execution context
            // This way i will be freezed in to the execution context
    );
  }

  return arr;
}

var fs2 = buildFunctions2();

fs2[0]();
fs2[1]();
fs2[2]();

console.log('---------------');

function buildFunctions3() {
  var arr = [];
  for (var i = 0; i < 3; i++) {
    let j = i;
    arr.push(
      function () {
        console.log(j); // using the keyword let in ES6, j is scope to the block,
                        // everytime a new j in memory is created,
                        // console.log(j) will pointing to a diffrent memory space for j
                        // that has the value 0, 1, 2
      }
    )
  }
  return arr;
}

var fs3 = buildFunctions3();

fs3[0]();
fs3[1]();
fs3[2]();



console.log('--------------------------------');

// Another classic case on closure
// See the stackoverflow thread for more info
// http://stackoverflow.com/questions/750486/javascript-closure-inside-loops-simple-practical-example

function temp(i) {
  setTimeout(function() {
    console.log(i);
  }, 2000)
}

// classic Javascript
for (var i = 0; i < 3; i++) {
  temp(i);
}

for (var i = 0; i < 3; i++) {
  setTimeout(function() {
    console.log(i);
  }, 2000);
}

// ES6 with let keyword
for (let i = 0; i < 3; i++) {
  temp(i);
}

for (let i = 0; i < 3; i++) {
  setTimeout(function() {
    console.log(i);
  }, 2000);
}