# function Define methods

// function without arguments

function sum() {
// code
}

const sum = () => {
// code
}

const sum = _ => {
// code multi line
}

const sum = _ => { /* single line */}

const sum = _ => console.log("single")

// function with arguments

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

const sum = (a, b) => {
return a + b;
}

const sum = (a, b) => a + b;

// function arguments with default Value, ES6

const sum = (a, b = 10) => a + b;

sum(10, 20) // 30
sum(20) // 30

// void function | non return
function print() {
console.log("print");
}

print()

// return function
function print() {
return "My console";
}

console.log(print());

function sum(a, b) {
// code
// code
// code
return a + b; // Number final result
return "stringsdf" // string
return true|false // Boolean
return [1,2 3,] // array
return {
// object
}
}

sum(5, 5) // 10;

// Object function
const Car = {
color: "blue",
move: function() {

}
}
// object function shorthand
const Car = {
color: "blue",
move() {

}
}

// closure function
function increment() {
let start = 0;

return function() {
return start++;
}
}

const store = increment();
store() // 0
store() // 1

// recursion
// !5 => 5+4+3+2+1
// !10=> 10+9+.....+1
function Factorial(n) {
if (n === 0) {
return 1;
}

return n * Factorial( n - 1 );
}

function sum(a){
return function(b) {
return function(c) {
return a + b + c;
}
}
}

sum(10)(20)(30) // 60

sum(10)
=> function(b) {
return function(c) {
return a + b + c;
}
}

sum(10)(20)
=> function(c) {
return a + b + c;
}
sum(10)(20)(30)
=> a + b + c = 60
map, filter, reduce

map=
callback(element, index, array)

const num = [1, 2, 3, 4];

// Array = [1, 2, 3, 4];
// Element 1, 2, 3, 4
// Index 0, 1, 2, 3

const num2 = num.map((item) => {
return item * 2
})
const num2 = num.map(item => item * 2)
// [2, 4, 6, 8];

function map(array, callback) {
const newArray = [];
for (let i = 0; i < array.length; i++) {
newArray = callback(array[i])
}
return newArray;
}