suhailgupta03

function greet(message, username) {
    // undefined are FALSY values in JS
    // !undefined means !false -> true
    if(!username) { // if username is not yet defined
        username = "user"; // we are assinging it some value
    }
   var greetMessage = `Hello, ${username}! ${message}`;
   console.log(greetMessage);
}
greet("Good evening");

suhailgupta03

var totalSum = 0; // this is variable with global scope

function sumTwoNumbers(x, y) {
    if(!y) { // this checks if y is undefined
        // if y is undefined, it will not
        // enter if block
        totalSum = totalSum + x;
    }else {
        totalSum = x + y;
        // here total sum becomes 300

suhailgupta03

var x = undefined;
console.log(x); // undefined
console.log(!x); // undefined in JS is a FALSY value
// !false means true

if(!x) { // since this is true, it will execute if block
    console.log("inside if");
}else {
    console.log("inside else");
}

suhailgupta03

function sum(x, y) {
    var z = x + y;
    return z; // return back the value of 
    // z
}

var zz = sum(5 , 6);
// sum(5 , 6) evaluates to 11
// sum(10, 20) evaluates to 30
console.log(zz);

suhailgupta03

var x = 7;

console.log(x); // 7
console.log(y); // undefined

var y; // Because of hoisting, the variable y
// will be PULLED upwards just before the program 
// starts its execution

suhailgupta03

sum(); // sum func will be pulled up b.cz of hoisting
mult(); // mult func will be pulled up b.cz of hoisting
div(); // the division function will be pulled up because of
// hoisting


function sum() {
    console.log("sum");
}

suhailgupta03

var zz = function(x, y) {
    return x + y;
} // Arjun created this general definition (anonymous) for other
// developers

var addTwoNumbers = zz; // Aditi says, that I will start 
// using zz to add two numbers, but before I will give it 
// a proper name
var result = addTwoNumbers(1, 2);
console.log(result);

suhailgupta03

var xx = () => {
    return "hey there!!"
}

var f = xx();
console.log(f);

suhailgupta03

function multiply(a, b) {
    return a * b;
}

function square(n) {
    return multiply(n, n);
}

function printSquare(n) {
    let result = square(n);

suhailgupta03

function greet() {
    console.log("Good evening"); // print the message
    greet(); // call greet function
}

greet();