A few simple Examples in EcmaScript6 to play around with.

EcmaScript6_Examples.js

const PI = 3.1415926535;


function foo(a = 123, b = '') {
    return PI
}


function bar(a, b, c, ...x) {
    return x.length;
}


class Animal {
    constructor(name, sex, weight = 0) {
        this.name = name;
        this.sex = sex === 'male' ? sex : 'female';
        this.weight = weight;
    }

    move(distance){
        this._distance += distance;
    }
    get distance() { return this.distance}
}


class Dog extends Animal {
    constructor(name, sex, weight, race, toy, ...optionalData) {
        super(name, sex, weight);
        this.race = race;
        this.toy = toy;
        this.optional = optionalData;
    }
    static bark(msg = 'Whooooof!!!') {
        return msg;
    }

    sprint(distance){
        Dog.bark('Sprinting!!!');
        this.move(distance);
    }
}


var dog = new Dog('Bello', 'male', 23);

dog.sprint(50);





function promiseExample() {
    return Promise((resolve, reject)
            => {setTimeout(() => resolve('msg'), 100)})
}


//Currencies:
var toEuro = Intl.NumberFormat('de-DE', {style : 'currency', currency: 'EUR'});
var toDollar = Intl.NumberFormat('en-US', {style : 'currency', currency: 'USD'});

toEuro.format(123456.457);
toDollar.format(123456.457);



function letExample() {
    console.log(x);
    var x = 123; //undefined

    console.log(y);
    let y = 456; //ReferenceError: y is not defined
}


//Dates:
var i10nEN = new Intl.DateTimeFormat("en-US");
var i10nDE = new Intl.DateTimeFormat("de-DE");
i10nEN.format(new Date("2015-01-02")) === "1/2/2015";
i10nDE.format(new Date("2015-01-02")) === "2.1.2015";


var sum = (x,y) => x + y;
var returnObject = id => ({id: id, msg: 'foo'});