functions.js

// console.log("h");
// console.log("i");
// console.log("m");
// console.log("a");
// console.log("n");
// console.log("s");
// console.log("h");
// console.log("i");

// function declaration
function sayMyName() {
console.log("h");
console.log("i");
console.log("m");
console.log("a");
console.log("n");
console.log("s");
console.log("h");
console.log("i");
}

// sayMyName // function reference
// sayMyName() // function execution

//function defination mein jo input variables lete h wo parameters hote h 
//jo function call pe values pass krte h wo arguements
function addno(num1, num2) {
    console.log( num1 + num2)
}

// addno(3,4);//7 //function call pass arguements
// addno(3,"4"); //34
// addno(3,null);//3

function addNo(no1, no2) {
    let result = no1 + no2;
    return result
    // return no1 +no2
}
// console.log(addNo(2,3));
const ans = addNo(5,4)
// console.log(ans)

//diff diff way to pass values

// function loginUserMessage(username) {
//     return `${username} just logged in`;
// }
// loginUserMessage("himanshi") 
//console.log(loginUserMessage("himanshi")) //print the returned value
// console.log(loginUserMessage(""))// empty String
// console.log(loginUserMessage()) // return undefined

function loginUserMessage(username) {
    if(!username) {
        console.log("pls enter user name");
        return;
    }
    return `${username} just logged in`;
}
// loginUserMessage("himanshi")
// console.log(loginUserMessage())
// bydefault value bhi store kr skte h username = "sam" as parameter

//funtions with object and array

//use rest operator (...num)
function calculateCartPrice(...num){
    return num ;
}
 
// console.log(calculateCartPrice(200,300,400,2000)) //output [200,300,400,2000]
//if we pass multiple values to perameter it will contain the first value
//to solve this problem we can use rest opetator(...num) it is diff from spread operator it stores all the value in an array

const user = {
    username : "himanshi",
    price : 199
}

function handleObject(anyobject){
    console.log(`username is ${anyobject.username} and price is ${anyobject.price}`)
}
// handleObject({
//     username: "himanshi",
//     price : 199
// })
// handleObject(user)

// function with array

const myNewArray = [200,300,400,2000]
function returnSecondValue(getArray) {
    // for(let key in getArray) {
    //     console.log(`price is ${getArray[key]} `);
    // }
    return getArray[2]
}
// returnSecondValue(myNewArray)
// console.log(returnSecondValue(myNewArray))

// block sope and global scope
// parent variables child access kr sakta h

function one() {
    const username = "hitesh"

    function Two() {
        const website = "youtube";
        console.log(username);
    } 
        // console.log(website);
        console.log("himasnhi");
        Two()
}
// one()

if(true) {
    const username = "himanshi"
    if(username === "himanshi") {
        const website = " youtube"
        // console.log(username + website)
    }
    // console.log(website);
}
// console.log(username)

// +++++++++++++++++++++++++++ interesting
// two way of creating functions 

// console.log(addone(5))
function addone(num) {
    return num + 1
}
// if we call a function before declaration the function will execute 

// addTwo(5)
const addTwo = function(num) {
    return num + 2
}
// functions hoisting
// if we assign a function in a variable and call that function variable before function declaration it will give error

// this keyword refers to the current context  with in a object
const user1 = {
    username : "hitesh",
    price : 999,

    welcomeMessage : function() {
        console.log(`${this.username}, welcome to website`) 
    console.log(this);
    }  
}

// user1.welcomeMessage()
// user1.username = "himanshi" //value change 
// user1.welcomeMessage();
// console.log(this)  // output empty object curly braces {}

// 
// this keyword not in use in function
// function chai() {
//     const username = "himanshi"
//     console.log(this.username); // output undefined
// }
// chai()

// const chai = function() {
//     const username = "himanshi"
//     console.log(this.username);
// }
// chai()

// arrow function

const chai = () => {
    const username = "himanshi"
    console.log(this);
}
// chai()

// expleset return means using return keyword
// const add1 =(num1 , num2) => {
//     return  num1 + num2
// }

// impleset return (for single line statement)
// const add1 =(num1 , num2) =>  num1 + num2

// without using return keyword using parentheses
// const add1 =(num1 , num2) =>  (num1 + num2)
// console.log(add1(3,2))

// object return krne k liye curly braces me wrap krte h jo is way mein krnge
const add1 =(num1 , num2) =>  ({username: "himanshi"})
// console.log(add1(3,2))

const myArray = [2,46,5,7,54]
// classic function
myArray.forEach(function() {
})

// arrow function
myArray.forEach(() => {
})

// IIFE immediately invoked function expretions
// first parentheses and second parentheses()()

function chai1() {
    console.log(`DB CONNECTED`);
}
// () //immediately invoke 
// chai1()

// global scope k pollution se problem hoti h to uske variable declaration se backne k liye block use krte h parenthesis laga k
// to imediately invoke a funtion we can write a funtion inside parenthesis to create a block

// (function chai1() {
//     // named iife bc function has name ie chai1
//     console.log(`DB CONNECTED`);
// }) ()  ; // at the end use semi colon to end the line


// ( (name) => {
//     // simple iife  unnamed iife
//     console.log(`db connected ${name}`)
// })("himanshi");


// js execution context + call stack 
// {}  // global EC

// last in first out LIFO concept 
// function call inside function
// call stack //inside dev tool sources create new snipet to check the call stack

function one() {
    console.log(`one`)
    two()
}
function two() {
    console.log(`two`)
    three()
}
function three() {
    console.log(`three`)
}
one()
two()
three()