JavaScript ES6 Classes and Arrow Functions

I try to understand difference between function expression, shorthand method definition, arrow function and bind().

Notice that I defined sayGoodBye() function in constructor, it means that whenever i create a new instance from this Person class, sayGoodBye() function will be defined for every instance.

sayHello() function is defined as a class property. But, as you can see in the following screenshot, class properties are also defined in constructor so class properties are just a sugar syntax.

getFullName() function is defined as shorthand method definition. But, Babel didn't move function definition in class constructor. So, if we use shorthand method definition in class, it will be a prototype function .

It mean they are only defined once, instead of once per instance.

Notice that in below screenshot, getFullName() function is in prototype of Person class, but sayHello() and sayGoodBye() are not.

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JavaScript Object.assign(), Object.create()


The Object.create() method creates a new object, using an existing object


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JavaScript Object.entries(), Object.values(), Map, Set Usage


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ES6 (ECMAScript 2015) Class Usage

There are some new features in ES6(ECMAScript 2015) like the following. But, we will focus on classes.

  • JavaScript let
  • JavaScript const
  • JavaScript Arrow Functions
  • JavaScript Classes
  • Default parameter values
  • Array.find()
  • Array.findIndex()

Class Declaration Syntax

Instance properties must be defined inside of class methods.

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Node.js Babel 7.x different usage transpiling to ES5 and Debugging

I already mentioned many details in the following link. So I don't want to duplicate everything in this post one more time.

You can reach github project from the following link.

You can reach Babel 6.x post from the following link.

Creating Babel configuration file


  "presets": [
  "plugins": [
  "env": {
    "development": {
      "presets": [
            "development": true
      "sourceMaps": true,
      "retainLines": true

JavaScript Promise and Async/Await

Asynchronous functions always return a Promise. So, I added following promise example firstly.

Promise Examples

The following three examples are doing same job. I used function statement and arrow function in Promise.

Promise with Function Declaration(Function Statement)

Promise with Arrow Function

Async Examples

Async Function Declaration(Function Statement)

Async Function Expression

Async Arrow Function

Await Examples

JavaScript – ECMAScript

I finally decided to write this post as well. I have collected many information from different links. When I need to remember fundamentals of JavaScript, I spend too much time in google. Because many developers just focused on specific features of JavaScript. In addition to this, different naming conventions are used, even they are mentioning about same topic 🙂
So, this is very very useful post for me. I hope that it will help any developers who need this kinds of collective documentation.

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