suhailgupta03

// closure is a function having access to the parent 
// scope
function greet() {
    var message = "Good evening";

    function sayHi() {
        console.log(message);
    } // Here closure is created, 
    // sayHi function has access to message variable

suhailgupta03

// setInterval(function() {
//     console.log("Playing MP4");
// },500); // continuous loop 
// // every 500 ms, it will print "Playing MP4"

setTimeout(function() {
    console.log("Downloaded MP4");
}, 3000); // 3s

suhailgupta03

setInterval(function() {
    console.log("Playing MP4");
}, 1000);

// the first argument is the callback 
// function
// the reason we call it as a callback
// function is because it is called back
// after a certain time interval

suhailgupta03

console.log(x);
var x = 1;
// Here x is undefined
// because JavaScript hoists declarations
// which means that the declaration is 
// automatically moved to the top of 
// the current scope

greet();
// greet function is hoisted

suhailgupta03

function calculator(operation, a, b) {
    if(operation == "add") {
        return a + b;
    }else if(operation == "subtract") {
        return a - b;
    }else if(operation == "multiply") {
        return a * b;
    }else if(operation == "divide") {
        return a / b;
    }else {

suhailgupta03

let numbers = [100, 0, 99, -1, 999, 4]
let sorted = numbers.sort((a, b) => a - b); // by default sort sorts in ascending order

// when a - b > 0, this means a > b, so a should be after b
// which means that larger number a should be after smaller number b
console.log(sorted)

let sortedDesc = numbers.sort((a, b) => b - a); // sort in descending order
// when b - a > 0, this means b > a, so b should be after a
// which means that larger number b should be after smaller number a

suhailgupta03

let i = 0;

function greet() {
    i++;
    console.log("Hello, World! ", i);
    if( i >= 500) {
        return;
    } // it is very important to have a base case
    // if you do not have a base case, you will
    // have an infinite loop

suhailgupta03

// IIFE
// Immediately Invoked Function Expression

(function() {
    var x = ".."
    var y = "...."
    var z = "......"
    console.log(x)
    console.log(y)
    console.log(z)

suhailgupta03

// function sum(a, b) {
//     return a + b;
// }

// const x = function sum(a, b) {
//     return a + b;
// }  // function expression
// // because it is assigned to a variable

const x = function (a, b) {

suhailgupta03

// function sum(a, b) {
//     return a + b;
//  }
// let v = sum(99, 1);
// console.log(v);

var x = function sum(a, b) {
    return a + b;
  } // x is a function
  // the reason x is a function is because it is a