Introduction

In this tutorial, we'll dive into the exciting new features introduced in ES6 (also known as ECMAScript 2015), the sixth version of the ECMAScript standard. ES6 brings a set of new capabilities and syntactic sugar that makes JavaScript more powerful and easier to read and write.

By the end of this tutorial, you will have a solid understanding of ES6 features such as:
- Arrow functions
- Promises
- Classes
- Modules
- Default parameters
- Destructuring assignment
- Template literals
- etc.

This tutorial assumes you have basic knowledge of JavaScript. If you're completely new to JavaScript, you might want to get up to speed with the basics before proceeding.

Step-by-Step Guide

Arrow Functions

Arrow functions provide a new way to write functions in JavaScript. They are shorter and have a simpler syntax. The syntax looks as follows:

const functionName = (parameters) => { /* function body */ }

An example of an arrow function:

const greet = (name) => { 
  console.log(`Hello, ${name}!`);
}
// Expected output: "Hello, John!" when you call greet("John")

Arrow functions also have a 'lexical this' feature. It means that they do not create their own context, so 'this' has the same value as in the surrounding code.

Promises

Promises are used to handle asynchronous operations in JavaScript. They are an object which represent the eventual completion or failure of an asynchronous operation, and its resulting value.

let promise = new Promise(function(resolve, reject) {
  // executor
});

The executor function takes two arguments: resolve and reject – these are callbacks provided by JavaScript itself. Our code is only inside the executor.

Classes

JavaScript classes introduced in ES6 are a syntactic sugar over the prototype-based OOP. The class syntax is not introducing a new object-oriented inheritance model to JavaScript.

class MyClass {
  constructor() { ... }
  method1() { ... }
  method2() { ... }
  get something() { ... }
  set something() { ... }
}

Code Examples

Using Default Parameters

Default function parameters allow named parameters to be initialized with default values if no value or undefined is passed.

function multiply(a, b = 1) {
  return a*b;
}

console.log(multiply(5, 2));
// expected output: 10

console.log(multiply(5));
// expected output: 5

Destructuring Assignment

The destructuring assignment syntax is a JavaScript expression that makes it possible to unpack values from arrays, or properties from objects, into distinct variables.

let a, b, rest;
[a, b] = [10, 20];
console.log(a);
// expected output: 10

console.log(b);
// expected output: 20

[a, b, ...rest] = [10, 20, 30, 40, 50];
console.log(rest);
// expected output: [30,40,50]

Summary

ES6 has brought a lot of powerful features that can greatly enhance your JavaScript code. In this tutorial, we have covered arrow functions, promises, classes, modules, default parameters, destructuring assignment, and template literals.

To learn more about ES6, you can check out the MDN Web Docs.

Practice Exercises

1. Write an arrow function that takes two parameters, sums them, and logs the result.
2. Create a promise that resolves after 2 seconds and returns the string "Hello ES6".
3. Write a class Person with a constructor that takes a name and age. The class should also have a method greet that logs "Hello, my name is [name] and I am [age] years old."

Solutions:

1. Arrow Function
   javascript const sum = (a, b) => console.log(a + b); sum(5, 3); // Expected output: 8

2. Promise
   ```javascript
   let promise = new Promise((resolve, reject) => {
   setTimeout(() => resolve("Hello ES6"), 2000);
   });

promise.then(alert); // Expected output: "Hello ES6" after 2 seconds
```

1. Class
   ```javascript
   class Person {
   constructor(name, age) {
   this.name = name;
   this.age = age;
   }

   greet() {
   console.log(Hello, my name is ${this.name} and I am ${this.age} years old.);
   }
   }

let john = new Person("John", 30);
john.greet(); // Expected output: "Hello, my name is John and I am 30 years old."
```

Keep practicing to become more familiar with these new features. Happy coding!