// Variable declaration

//automatically
a_ = 5; b_ = 6; c_ = a_ + b_;
console.log(c_);

// let , var , const
let a;
var b;
const c = 3.14;
a = 5;
b = 4;
b = 6;
z = a + b + c;
console.log(z);

//var
var x = "om";
var x = 0;
console.log(x);
x = 5;
console.log(x);
var x = 8;
{
  var x = 10;
}
console.log(x);
//Hoisting but not with let or const : ReferenceError
carName = 'bmw';
var carName;
console.log(carName);

//let
let x1 = "om";
//let x1 = 0; error not redeclared
x1 = "hari";
console.log(x1);
let x2 = 2;
{
  let x2 = 10;
}
console.log(x2);

//const
const PI = 3.14;
console.log(PI);

//Arrays
const cars = ['audi', 'bmw', 'volvo'];
cars[0] = 'tata';     //change an element
cars.push('fortunar');    //add an element
/*
but cannot reassign : TypeError
cars = ['thar', 'jaguar'];
*/
console.log(cars);
console.log(typeof(cars));

//Objects
const car = {name : 'bmw', color : 'white', year : 2023};
car.color = 'black'; //change properties
car.owner = 'hariom'; //add properties
/*
but cannot reassign by using const & let : TypeError
car = {name : 'audi',color:'black'};
*/
console.log(car);
console.log(typeof(car));

var car1 = {name : 'audi', color : 'red'};
console.log(car1);

var car1 = {name : 'bmw', color : 'white'};
console.log(car1);

console.log(car1.name);

const person = {
  fname : 'hari',
  lname : 'om',
  fullname : function(){
    return this.fname + ' ' + this.lname;
  }
}

// String, Number, Boolean as Objects
o1_ = new String();
o2_ = new Number();
o3_ = new Boolean();

//Operations
// String Comparison
let s1 = 'ba';
let s2 = 'c';
let s3 = 'b';
let s4 = '5';
let s5 = '4';
let s6 = 8;
let s7 = 'caa';
console.log(s1 < s2);
console.log(s2 < s3);
console.log(s3 < s4);
console.log(s4 < s5);
console.log(s5 < s6);
console.log(s1 < s7);
console.log(typeof(s1));
console.log(typeof(s6));

let str = ' this is a string. ';
console.log(str.length);

let text = "Apple, Banana, Kiwi";
console.log(text.slice(7));
console.log(text.slice(7,13));
console.log(text.slice(-12));
console.log(text.slice(-12,-6));

console.log(text.substring(7));
console.log(text.substring(7,13));
console.log(text.substring(-12));

//substr(start, length)
console.log(text.substr(7, 6));

console.log(text.replace('Kiwi', 'Orange'));

//String to Array
console.log(text.split(','));

//Template Literals
let txt = `Hello back-ticks`;
console.log(txt);

//Interpolation & Variable substitutions
let fn = 'hari';
let ln = 'om';
let full = `${fn} ${ln}`;
console.log(full);

let xx = "100";
let yy = "10";
let zz = xx / yy;
console.log(typeof(zz));
let ss = zz.toString();
console.log(typeof(ss));
let nn = parseInt(ss);
console.log(typeof(nn));

let m = 'om';
let n = new String('om');
console.log(m == n);
console.log(m === n);
// object compare with object gives always false

let bo = true;
console.log(typeof(bo));

const date = new Date("2023-07-12");
console.log(date);

let xs = 'bmw' + 16 + 4;
console.log(xs);

let sx = 16 + 4 + 'bmw';
console.log(sx);

let un;
console.log(un);
console.log(typeof(un));

let bike = ''; //empty String

let arr = []; //empty Arrays
arr[0] = 'tvs';
arr[1] = 'honda';
console.log(arr);

// array to String
let na = arr.toString();
console.log(na);

//using objects
const ccc = new Array("Saab", "Volvo", "BMW");

let obj = {}; //empty Objects

// Array map() creates new array by performing a Functions
//on each array element
const num1 = [45, 4, 9, 16, 25];
const num2 = num1.map(funct);

function funct(value, index, array) {
  return value * 2;
}
console.log(num2);

//Normal Functions
function add(a,b){
  console.log(a+b);
}
add(3,4);

let xfm = multip(5,8);
console.log(xfm);
function multip(a,b){
  return (a*b);
}

//Arrow Function
let addi = (a,b) => a + b;
const ans = addi(4,7);
console.log(ans);

//Simple arrow 
hello = () => console.log("hello");
hello();

//Function Expression
const exp = function(a,b){
  return a*b;
}
let ex = exp(6,8);
console.log(ex);

//Function Constructor
const cons = new Function("a", "b", "return a * b");
console.log(typeof(cons));
let fc = cons(4, 3);
console.log(fc);
console.log(typeof(fc));

// Function Hoisting
let fh = myFu(5);
console.log(fh);
function myFu(y) {
  return y * y;
}

//Self - Invoking Functions
(function(){
  console.log("Self invoking");
})();

/* call & apply(args = array) method
const person = {
  fullName: function() {
    return this.firstName + " " + this.lastName;
  }
}
const person1 = {
  firstName:"John",
  lastName: "Doe"
}
const person2 = {
  firstName:"Mary",
  lastName: "Doe"
}
person.fullName.call(person1);

const per = {
  fullName: function(city, country) {
    return this.firstName + " " + this.lastName + "," + city + "," + country;
  }
}

const per1 = {
  firstName:"Hari",
  lastName: "Om"
}

per.fullName.apply(per1, ["lko", "India"]);
*/


// object Constructor
function Person(first, last, age, eye) {
  this.firstName = first;
  this.lastName = last;
  this.age = age;
  this.eyeColor = eye;
}
const myFather = new Person("John", "Doe", 50, "blue");
const myMother = new Person("Sally", "Rally", 48, "green");

//for...of
const arry = [1,2,3];
for(const j of arry){
  console.log(j);
}

//for...in
const pn = {firstName:"John", lastName:"Doe", age:50};
let s = '';
let ar = [];
//property print
for(let i in pn){
  console.log(i);
  ar.push(i);
}
console.log(ar);
//values print
for(let i in pn){
  s += pn[i] + ' ';
  ar.push(pn[i]);
}
console.log(ar);
console.log(s);

pn.color = "black";
console.log(pn);

//forEach()
/*  
const letters = new Set(["a","b","c"]);
let text = "";
letters.forEach (function(value) {
  text += value;
})
*/
const newarr = new Array('a','b','c');
let news = '';
newarr.forEach(function(val){
  news += val;
})
console.log(news);

//Comparison
let a8 = 10;
let b8 = "10";
console.log(a8==b8);
console.log(a8===b8);

let o1 = {a:1, b:2, c:3};
let o2 = {a:1, b:2, c:3};
console.log(o1==o2);
console.log(o1===o2);

const man = {
  firstName: "John",
  lastName : "Doe",
  id       : 5566,
  fullName : function() {
    return this.firstName + " " + this.lastName;
  }
};
console.log(man);

myObj = {
  name:"om",
  age:21,
  cars: {
    c1:"Ford",
    c2:"BMW",
    c3:"Fiat"
  }
}
console.log(myObj);
console.log(myObj.cars.c2);

let x8 = "John";
let y8 = new String("John");
console.log(x8==y8);

let x11 = "John";
let x21 = new String("John");
console.log(x11===x21);

// Template String
let firstName = "John";
let lastName = "Doe";
let tt = `Welcome ${firstName}, ${lastName}!`;
console.log(tt);

let x3 = 10;
let y2 = 20;
let z2 = "30";
let rt = x3 + y2 + z2;
console.log(rt);

// *,-,/ also but not + concat..
let xx1 = "100";
let yy1 = "10";
let z11 = xx1 / yy1;
console.log(z11);

//NaN
let x4 = 100 / "Apple";
console.log(x4);

//Functions
var cc = "Tata";
function myFunction() {
  let carName = "Volvo";
  console.log(carName);
  console.log(cc);
}
myFunction();
//console.log(carName);
console.log(cc);

myFunc();
console.log(car_);
function myFunc() {
  car_ = "BMW";
}

function toc(f) {
  return (5/9) * (f-32);
}
let v = toc(77);
console.log(v);

//func expression
var f = function(){
  console.log("function expression")
}
f();

function add(a,b){
  console.log(a+b);
}
add(4,5);

//Arrow Function
let arrFunc = (a, b) => a * b;
var ans1 = arrFunc(2,3);
console.log(ans1);

hello = () => {
  console.log("Hello World!");
}
hello();

//Function Hoisting
multi(5);
function multi(y) {
  console.log(y * y);
}

//Self-invoking function - function without name
(function () {
  console.log("I will invoke myself");
})();


// Scope & Hoisting
x5 = "Audi";
//let x5;
var x5;
var x5 = "Tata"
//const x5;
console.log(x5);

/*
const PI;
PI = 3.14;
console.log(PI);
*/

//spread operator
let a1 = [1,2,3];
let a2 = [...a1];
console.log(a1);
console.log(a2);
console.log(a1==a2);
console.log(a1===a2);

a1.push(4);
a1.unshift(0);
console.log(a1);
console.log(a2);
a1.shift();
a1.pop();
console.log(a1);
console.log(a2);

const myVehicle = {
  brand: 'Ford',
  model: 'Mustang',
  color: 'red'
}

const updateMyVehicle = {
  type: 'car',
  year: 2021, 
  color: 'yellow'
}

//color is overwritten
const myUpdatedVehicle = {...myVehicle, ...updateMyVehicle}
console.log(myUpdatedVehicle);

//rest - treats arguments as an array
function sum(...args) {
  let tsum = 0;
  for (const i of args) {
    tsum += i;
  }
  return tsum;
}
console.log(sum(1, 2, 3));
console.log(sum(1, 2, 3, 4));

//Closures
function out(){
  let a3 = 7;
  function inf(){
    a3 = 4;
    console.log(a3);
  }
  inf();
  console.log(a3);
}
out();

// Destructuring
const item = ['a','b','c'];
const [m11,n11,o11] = item;
console.log(m11);

let per = {name: "om", age:"21"};
let {name, age} = per;
console.log(name);
console.log(per.name);

console.log(per);
delete per.age;
console.log(per);

//Exception Handling
let g = 4;
try{
  g = h + 1;
  console.log(g);
}
catch(err){
  console.log("Error" + ': ' + err.name);
}
finally{
  console.log("Exception");
}

//Normal myCalculator
function display(res){      //res = 6
  return res;
}

function calculate(a,b){
  let cs = 0;
  cs = a + b;
  return cs;
}

let output = calculate(9,3);
//let out_ = display(output);   //output = 6
console.log(output);

//callback
function myCalculator(num1, num2, callback) {
  let sum = 0;
  sum = num1 + num2;
  callback(sum);
}
myCalculator(5, 8, result); //as an argument
function result(some) { //a callback function
  console.log(some);
}
//wrong : myCalculator(5, 8, result());
//In real world, callbacks are used with 
//asynchronous Functions eg.- setTimeout()

/*
const main = (callback) => {
  setTimeout(() =>{
    callback([1,2,3])       //callback function
  },1000)
}

const add = (arr) =>{
  let sum = 0;
  for(let j of arr){
    sum += j;
  }
  console.log(sum);
}

main(add); //argument
*/


//callbacks for addition of an array element
const mainfunc = (callback) =>{
  setTimeout(() =>{
    callback([1,2,3,4]) 
  }, 1000)
}

const addarr = (_arr) =>{
  let arrsum = 0;
  for(const j of _arr){
    arrsum += j;
  }
  console.log(arrsum);
}

mainfunc(addarr); //calling main function

/*callback *****
const mainfunc = (callback) =>{
  setTimeout(() => {
    callback([1]);
    setTimeout(() => {
      callback([2])
    }, 1000)
  }, 1000)
}
*/

/*Promises

let promise = new Promise(function(resolve, reject){
  resolve();  //Success
  reject();   //Error
});
promise.then(
  function(value);
  function(error);
);

*/

let mypro = new Promise(function(resolve, reject){
  let r = 10;        //Producing Code
  if(r == true){
    resolve("Success");
  }else{
    reject("Error");
  }
});
mypro.then(
  function(value){
    dis(value);
  },
)
.catch(
  function(error){
    dis(error);
  }
);
function dis(some){
  console.log(some);
}


//separator operator but not used at start or end
const sep1 = 1_000_000_000;
const sep2 = 1000000000;
console.log(sep1 === sep2);

//Symbol
let sym = Symbol("hello");
console.log(sym);
let sim = Symbol("id") == Symbol("id");
console.log(sim);
let cdm = "hello";
console.log(sym == cdm);

console.log(Array.from("ABCDEFG"));

//Default Parameter
function defpara(x, y=10) {
  // y is 10 if not passed or undefined
  console.log(x + y);
}
defpara(5);

let $1 = 1 + 1;
let $2 = 2;
console.log($1 == $2);

let $3 = 1.1 + 0.2;
let $4 = 1.3;
console.log($3 == $4);


//Time interval method
function fun(){
  for(let i=1; i<=5; i++){
    setTimeout(function() {
      console.log(i);
    }, 1000);
  }
  console.log("JavaScript");
}
fun();