function.js

// function = A section of reusable code.
//            Declare code once, use it whenever you want.
//            Call the function to execute the code.

// Printing function
function happyBirthday(userName, age){
    console.log("Happy Birthday to you ");
    console.log("Happy Birthday to you ");
    console.log(`Happy Birthday dear ${userName}`);
    console.log("Happy Birthday to you");
    console.log(`You are ${age}`);
}

happyBirthday("BroCode", 46);

// Return function
function add(x,y){
    return x + y
}

function subtract(x,y){
    return x - y
}

console.log(add(2,3))
console.log(subtract(2,3))

//callback = a function that is passed as an argument to
//            another function

//           used to handle asynchronous operations
//           1. Reading a file
//           2. Network Requests
//           3. Interacting with databases
//          "Hey when you're done , call this next"

// Asynchronous operations in JS are tasks that run in the background without
// blocking the main execution thread , allowing the program to remain responsive and handle
// other events concurrently.

hello(goodbye);

function hello(callback) {
    console.log("hello");
    callback();
}

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

sum(displayConsole, 1, 2)

function sum(callback, x, y){
    let result = x+y;
    callback(result);
}

function displayConsole(result){
    console.log(result);
}

// setTimeout function: first functionRef then lines of code and timeout
// time in Milliseconds

//forEach() = method used to iterate over the elements of an array
//            and apply a specified function (callback) to each element

//              array.forEach(callback), element, index, array are provided

let numbers = [1,2,3,4,5];

numbers.forEach(display)
numbers.forEach(double);

function display(element){
    console.log(element);
}

function double(element , index, array){
    array[index] = element * 2;
    console.log(array);

}

//.map() = method used to apply a callback to an array create a
//         new array storing the callback applied values.
//         It is similar to .forEach() function

let mappingNumbers = [1,2,3,4,5,6]
let mappedNumbers = mappingNumbers.map(cubed)

console.log(mappedNumbers)

function cubed(element){
    return Math.pow(element, 3)
}

//.filter() = method to create a new array by filtering out elements.
//            It keeps the element that return a 'true' boolean value
//            filters out the elements that return a 'false' boolean value

let nums = [1,2,3,3,4,5,2,3,4,6,4,];

let evenNums = nums.filter(isEven);
console.log(evenNums);
function isEven(element){
    return Number(element) % 2 === 0;
}

//.reduce() = reduces an array to one single value. It is the sum of the array.The accumulator
//            parameter is the previous value and the element is the next value in relation to
//            the accumulator.

let prices = [30, 40, 50, 80, 90, 20]

let bill = prices.reduce(sum_fx);
console.log(`$${bill}`);

let max = prices.reduce(getMax);
console.log(max);

let min = prices.reduce(getMin);
console.log(min);

function sum_fx(accumulator, element){
    return accumulator + element;
}

function getMax(accumulator, element){
    return Math.max(accumulator, element);
}

function getMin(accumulator, element){
    return Math.min(accumulator, element);
}

// function expression = a way to define functions as values or variables

//Example of defining functions as variables
const printHello = function(){
    console.log("Hello!");
}

printHello();

//Example of defining functions as values:
// Callbacks in asynchronous operations
// High Order Functions
// Closures
// Event Listeners

setTimeout(function(){
    console.log("Hello! This came 1 seconds later");
}, 1000); // 1 second later

//arrow functions = are used for writing function expressions in a concise way e.g. (parameters) => some code

const greet = (name) => {console.log(`Hello ${name}`)
                              console.log(`Your name is ${name}`)
};

greet("Sarthak Roy");

//destructuring = arrange values in a different order for convenience
//                [] for arrays
//                {} for objects

// Example 1 : Swapping values of variables

let numberA = 1;
let numberB = 2;

[numberA, numberB] = [numberB, numberA];
console.log(numberA);
console.log(numberB);

//Example 2 : Swapping elements of an array

const colors = ["red", "green", "blue", "black", "white"];

[colors[0], colors[4]] = [colors[4], colors[0]];

console.log(colors);

//Example 3: Assign array elements to variables

const colors1 = ["red", "green", "blue", "black", "white"];

let firstColor ;
let secondColor ;
let thirdColor ;

let extraColors;
[firstColor,secondColor, thirdColor, ...extraColors] = colors1;

console.log(firstColor);
console.log(secondColor);
console.log(thirdColor);
console.log(extraColors);

//Example 4 : Extract values from objects

const person1 = {
    name : "Sarthak Roy",
    age : 12,
    job: "Engineer"
}

const {name, age, job="Unemployed"} = person1;

console.log(name);
console.log(age);
console.log(job);

//Example 5: Destructure in function parameters

function displayPerson({name, age, job}) {
    console.log(name);
    console.log(age);
    console.log(job);
}

const person2 = {
    name : "Ankita Roy",
    age : 18,
    job: "Doctor"
}

displayPerson(person2);

//nested objects = Objects inside of objects which helps in making very complex data structures
//                  e.g. computerSetup{CPU{}, GPU{}, Motherboard{}}

const ComputerSetup = {
    place: "Sarthak's Room",
    core: "MI Notebook 14",
    CPU : {
        name: "Intel i3 10100U",
        clockSpeed: 2.10
    },
    GPU : {
        name: "Intel(R) UHD Graphics",
        GPUMemory: 3.9
    },
    RAMMemory : {
        memory: 8,
        type : "DDR4"
    }
}

console.log(ComputerSetup.place);
console.log(ComputerSetup.core);
console.log(ComputerSetup.CPU.name);

for (const property in ComputerSetup.CPU){
    console.log(ComputerSetup.CPU[property]);
}

for (const property in ComputerSetup.GPU){
    console.log(ComputerSetup.GPU[property]);
}