Es6 In a Nutshell

es6.js

// 1:)let
var name = "burak";
console.log(name);

//or use let
let name2 = "burak2";
console.log(name2);

// Why we would use let instead of var?
/* In js, there is global and local scope but js doesn't really have a
block scoping. For ex; */
var animal = "cat";
if (true) {
	//var animal="bird";
	let name = "bird";
}
console.log(animal); //if var is used, output is bird.
/* But if we use let, the output will be cat.Cos, the variable has block
scoping inside the curl braces */

// Pro let tip;
function sayName() {
	age = 22;
}
let age;
sayName();
console.log(age);
//This works.Cos we declared let variable before calling the sayName() function



// 2:)const
const COLOR = "black";
console.log(COLOR);
/*
This variable is constant. It may not be changed.For ex if i wanna reassign
the variable, i get error. 
Constants can be declared uppercase or lovercase but mostly used uppercase.
*/
const AGES = [1, 2, 30];
console.log(AGES);
// But we can push new value to an array!



// 3:)functions
function lol2() {
	console.log("I called 2.");
}
lol2();
//In es6 we can write it like that;
var lol3 = () => {
	console.log("I called 3.");
};
lol3();

setTimeout(() => {
	console.log("I am setTimeout output.");
}, 4000);



// 4:)Template Literals
let myname = "Burak"
let xx = "This is a string.";
// That is back tick => `
let xx2 = `
first line
Multi line string! 
`;
console.log(xx2);
// Also we can use variable inside it;
let xx3 = `
my name is ${myname}
`;
console.log(xx2);



// 5-)Extract values from array easily
let numbers666 = [1, 2, 3];
let [a, b] = numbers666;
console.log(a); //output is 1
console.log(numbers666); //output is [1,2,3]

//if we want to get part of an array, we can do like this;
let [x, ...y] = numbers666;
console.log(y) //output is [2,3]

// and we can add the numbers666 array values,
function add(a, n, c) {
	console.log(a + n + c);
}
add(...numbers666); // output is 6

// we can also merge 2 arrays together easily
var fruits = ["banana", "kiwi"];
var sports = ["football", "tennis", "basketball"];

// if we want to put fruits array after football, we can just do like that;
var sports = ["football", ...fruits, "tennis", "basketball"]; // thats it!



// 6-) Classes
class Person {
	constructor(name, age) {
		this.name = name;
		this.age = age;
	}
	displayAge() {
		console.log(this.age)
	}
}
let burak = new Person('Burak', 22);
burak.displayAge();

// Inheritance
// We grabbed all the codes of Person class and also we can add new attributes here;
class Programmer extends Person {
	//language added additionally
	constructor(name, age, language) {
		super(name, age) // we already have that attributes
		this.language = language;
	}
	displayLanguage() {
		console.log(this.language);
	}
}
let mehmet = new Programmer("Mehmet", 23, "JavaScript");
mehmet.displayAge();
mehmet.displayLanguage();



// 7-) Array Iteration

var arr = ['a', 'b', 'c'];

for(let i of arr) {
   console.log(i)	
}




// *** === More === *** //

// 1-) Computed property names
// We can not do this in ES5
var obj = {};
obj[prop] = 'some value';
// If we want, we have to do like this!
var obj = {
	[prop]: 'some value'
};

// 2-) Default parameters
// This syntax is often used to give function parameters default values. Even when you do know this syntax, it fails spectacularly when dealing with booleans, numbers or other falsy values. 
function hello(name) {
	name = name || 'Anonymous';
	console.log('Hi ' + name);
}
//In ES6, we have default parameters also:
function hello(name = 'Anonymous') {
	console.log('Hi ' + name);
}

Line 130 should be console.log(this.language) instead of console.log(language)

@balamalireddi thank you, fixed it! 👍