arrowFunctions.js

//ES5
function add(x, y) {
    return x + y;
}

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

// arrow function

const Sum = (x, y) => x + y;
console.log(Sum(3, 4));


//arrow function with no arguments
const multiply = () => (5 * 8);
console.log(multiply());

//arrow function with single argument
const subtract = x => --x;
console.log(subtract(4));


// arrow function with returning the object should wrap with braces
const obj = () => ({ name: 'yamini', address: 'tenali' });
console.log(obj());


//arrow function with object's inner nested objects
let productname = '';
function addToCart() {
    this.productname = 'Laptop';

    // ES-5 Approach 
    this.getProduct = () => {
        console.log('34>>>', this);
        const that = this; // we need to store the reference of 'this' in another variable in order to get execute the inner nested function efficiently.
        setTimeout(function () {
            console.log('37>>>>>>', that);
            console.log(that.productname);
        });
    }

    // ES-6 Approach
    this.getAllThings = () => { // here 'this' wont work as it will takes as 'this' from the outer scope as it is referring to the window object
        console.log('45>>>>>', this);
    }

    this.getThing = function () {
        console.log(this);

        setTimeout(() => { //arrow function will refer to the parent function 'this' context if it is a inner nested loop
            console.log('48>>>>>', this);
        })
    }
}

let objj = new addToCart();
console.log(objj.getProduct());
console.log(objj.getThing());

/* Note: Arrow functions doesnot have its own 'this' */


//arguments
// with function it would return the arguments 
function abc() {
    return console.log('arguments>>>>>', arguments);
}

console.log(abc(3, 4, 5));

// without rest operator fat arrow functions won't return the value.
const abcd = () => {
    console.log('arguments2>>>>>', ...arguments); // Reference Error : arguments is not defined.
}

console.log(abcd(7, 8, 9));


let myFunc = {
    showArgs: () => {  // here 'this' wont work as it will takes the 'this' from the outer scope as it is referring to the window object
        console.log('showArgs', ...arguments);
    },
    showAbc: function () { // here 'this' will work as it is referring to the object scope
        console.log('showAbc', ...arguments);
    }
};
myFunc.showArgs(1, 2, 3, 4);

const names = ["sam", "daniel", "peter"];
const result = names.map(r => r.toUpperCase());