Top 7 JavaScript Playgrounds to Use in 2019

Top 7 JavaScript Playgrounds to Use in 2019

Top 7 JavaScript Playgrounds to Use in 2019

The importance of online code editing platforms cannot be overemphasized. As much as we love our local IDE’s, one too many times we find ourselves needing to quickly share and or collaborate with a friend or colleague in our local projects.

Table of Contents

In cases like this, online playgrounds give us that added functionality to write and run codes as well as share snippets and have colleagues test it out and give us feedback. In this post, we’ll be looking at the top 5 online code editors for JavaScript in no particular order.

CodePen

CodePen is an online social development environment for front-end developers. It comes fully equipped with all the features you’ll need to build, test, share, collaborate and even deploy your websites.

Plans and Features CodePen plans are flexible enough to accommodate whatever needs you might have. First, there are individual and team plans. Under the individual plans, you have a range of other plans that have been carefully structured to offer you a wide range of choices depending on what features are more important to you and on how much you can afford.

The free plan has all you need to perform usual operations like creating pens, sharing snippets, running tests and so much more. If you’re developing for experimental purposes or just building out your project for development purposes, the free plan has all you need.

The PRO plan, however, adds a little bit to what you can do with CodePen. With CodePen PRO, you get unlimited privacy, asset hosting space, live view, embedded themes and so much more. On the PRO plan, you won’t miss your local IDE. If you have specific needs for these features and you’ve got a few dollars to spare, then these plans are totally worth the price.

You can visit the pricing page to have a closer look at what each plan offers to help you decide. However, that’s not all, as we mentioned earlier, there’s also a team plan for people working in teams. The price of the team plan is subject to the number of members in your team. However, it comes with a standard $12/month/member price.

CodeSandbox

CodeSandbox is an online editor that allows developers to focus on writing code while it handles all the necessary background processes and configurations. Unlike CodePen, CodeSandbox focuses more on building and sharing code demos that contain back-end components. The editor is optimized to analyze npm dependencies, show custom error messages, and also make projects searchable by npm dependency.

CodeSandbox offers dedicated sandboxes to help developers quickly get started on developing with their favorite tools to build web applications. With CodeSandbox, all you need to do is open the browser, select your preferred development tool and start writing code. It abstracts all the backgrounds tasks and configurations so that you only need to worry about writing your code. With Condesandbox, we can do all of the following and more:

Github integration With Codesanbox 2.0, you can commit, create repositories and open pull requests right from within CodeSandbox.

Host static files CodeSandbox hosts all the files in the public directory for you. Previously this functionality didn’t exist on CodeSandbox, but now, you can add static images, web workers, etc. As a result, you can imitate all the functionalities of your local development server as you now have full access to the index.html file.

Real-time collaboration With CodeSandbox, you can create a project and open a Live Session to generate a live URL you can share to colleagues. Through the URL, all your colleagues can work together on the project at the same time. This may seem difficult to manage when the number grows, and you can’t track what each person is doing. As a result, you can switch to a Classroom Mode where you can specify who can edit the sandbox and who can only view.

Visual studio code integration CodeSandbox has a feature called VSCode in browser. It allows you access to VSCode features like keybindings, user snippets, breadcrumbs etc. All you need to do is copy your settings files directly from VSCode to CodeSandbox, and you will have control of all the files on your sandbox. These are only a handful of the features you’ll get with CodeSandbox, there are more, like working in teams, Sandbox containers etc. I invite you to check them out their docs page for more.

Back-end support

It is worthy to note that CodeSandbox is one of the few online playgrounds that has support for back-end languages like Node.js. What’s more? It has npm support. As a result of it, you can install any npm package you require in seconds.

StackBlitz

StackBlitz is a VSCode powered online playground for web developers. It offers developers the ability to create projects in just one click. The collaboration features of StackBlitz makes it possible to share a created project with colleagues through a unique project URL.

Seamless project setup Like other playgrounds we’ve already mentioned, StackBlitz automatically takes care of all the background processes involved in setting up projects; like installing dependencies, compiling, bundling, etc. This way it abstracts the setup process for you so you can focus on what you do best, writing code. Stackblitz is renowned for its ability to handle Angular and React projects, all you need to set up a new of them is the click of a button.

VSCode similarity Because VSCode powers StackBlitz, it comes packed with all the Aesthetic features we love in VSCode, giving you the look and feel of your local IDE.

TypeScript support StackBlitz has TypeScript support and TypeScript auto-completion, a feature that is not found in other IDE’s like Plunker.

NPM support With StackBlitz, you can import any npm package into your project, just like you would in VSCode. Better still, you can copy snippets from documentation pages and blogs into the editor and it’ll automatically detect the missing packages and prompt you to install them.

Image credit to Eric Simons.

Offline support Thanks to StackBlitz in-browser development server, you can continue writing code and editing your work even when offline. This gives you the superpower to build offline while leveraging the power of the online platform, killing two birds with one stone. We can’t possibly go over all the perks, but you’re welcome to see them yourself on the website.

JS Fiddle

JSFiddle is an online playground for creating, testing and showcasing collaborational HTML, CSS and JavaScript code snippets, known as ‘fiddles’. It is one of the earliest playgrounds that laid the foundation for the creation of other modern-day playgrounds. At the moment, it may seem a bit basic compared to modern playgrounds like CodePen; however, it still performs basic playground operations like testing, sharing, and collaboration. As an added advantage, JSFiddle can also perform complex ajax simulations.

JSFiddle lets you quickly get started by providing access to unique boilerplate templates for diverse technologies. As a result, it’ll take you just about the click of a button to generate a boilerplate code for React, Vue or whichever technology you want.

As much as JSFiddle behaves alike with other playgrounds, it has certain features that make it equally unique in its own way. Unlike most others, with JSFiddle, you can customize, add and use other JavaScript tools and frameworks easily. With the Togetherjs support, JSSFiddle offers an interactive user interface that lets users collaborate and share fiddles with colleagues. Moreso, it has inbuilt Git support. You can also use JSFiddle for any of the following:

JS BIN

JSBin is a live playground for Html, CSS and JavaScript and a range of other preprocessors like jade, markdown and much more. It provides specific editor panels with an intuitive user interface for user interactivity. With JSBin, users can create bins, share, collaborate and test codes.

JSBin is mostly focused on the ability to share code. It shares not just the code but also the complete output result of the code in the bin. It’s real-time collaboration features lets colleagues view and see changes in real-time as you type in the editor panels.

Though JSBin opens into a default Html code on start, there are many libraries available for you. You can add as many libraries as is required for your project to build your desired product.

With JSBin, all created bins have a unique sharing Url that other users can join with to collaborate, fork and or edit the bin, while your original bin remains intact. Moreso, with JSBin, you can perform the following operations and more

JSBin also has a PRO plan that adds more functionality to what you can do. It gives an additional layer of features to extend your bin functionality. With The JSBin PRO, you can

Scrimba

Scrimba is an entirely different kind of online playground than what we’ve seen so far. It offers you the ability to pause the video and edit the instructor’s code and see the result in the editor.

In-video interaction This provides an extra layer of interactivity to the usual playground functionality. Scrimba lets you take up an instructors demo and build it up into whatever use case you desire. In the playground mode, you can interact with the instructor’s code however you please, and you can edit, copy, paste and basically perform any interactive operation you desire.

Cross-platform Scrimba is completely cross-platform. It adapts to any screen size and arranges contents in both portrait and landscape mode to match your screens resolution requirements, this way, it constantly serves you the best visual output.

Console and dependencies Scrimba has an in-built console that both the user and the instructor can access to run commands and debug code. You can log messages just the same way you would in any other editor. It also lets you install external dependencies into your project. What’s better? the Scrimba team has designed the console in a way that you can see the console output with opening the console panel.

Analytics Scrimbar has a sidebar notes features that track all the changes you make in the editor. This is a handy feature that gives you the ability to keep track of all your changes and refer to them in the future when the need be.

Liveweaver

Liveweaver is an online playground for Html, CSS, and JavaScript for web designers and developers. Like other editors we’ve come across, Liveweaver gives users the ability to create, test, and share code with colleagues.

It opens into distinct editor panels for Html, CSS, JavaScript and Output panels respectively. One remarkable feature of Liveweaver is its simplicity. A newbie could easily open up Liveweaver, create a small app and run it without reading up any prior documentation.

Moreso, Liveweaver supports a wide range of third-party libraries like Bootstrap, jQuery, Threejs etc. This helps developers build more robust applications without library support hinderances.

Liveweave is free to use and comes packed with over 20 handy JavaScript libraries. With Liveweave, you can do all of the following and more

Conclusion

In this post we have discussed five top online JavaScript editors you can use in 2019. Each playground has it’s unique abilities so its difficult to choose a “best” one amongst them. We can, however, choose the one whose features best solves our needs. Disclaimer: This five online playgrounds discussed here are entirely my choice based on my own experience with them. There are other amazing online playgrounds like Plunker, CSS Deck, Dabblet, etc. If you have other playgrounds in mind, please do share them with us in the comments below. Hopefully, this post would help you pick the most suitable one for your needs.

What is JavaScript – All You Need To Know About JavaScript

What is JavaScript – All You Need To Know About JavaScript

In this article on what is JavaScript, we will learn the basic concepts of JavaScript.

After decades of improvement, JavaScript has become one of the most popular programming languages of all time. It all started in the year 1995 when Brendan Eich created JavaScript in a span of 10 days. Since then, it has seen multiple versions, updates and has grown to the next level.

Here’s a list of topics that I’ll be covering in this blog:

  1. What is JavaScript
  2. What can JavaScript do?
  3. JavaScript Frameworks
  4. The Big Picture: HTML, CSS & JavaScript
  5. Benefits of JavaScript
  6. Fundamentals of JavaScript
    VariablesConstantsData TypesObjectsArraysFunctionsConditional statementsLoopsSwitch case
What is JavaScript?

JavaScript is a high level, interpreted, programming language used to make web pages more interactive.

Have you ever thought that your website is missing something? Maybe it’s not engaging enough or it’s not as creative as you want it to be. JavaScript is that missing piece which can be used to enhance web pages, applications, etc to provide a more user-friendly experience.

What is JavaScript?

JavaScript is the language of the web, it is used to make the web look alive by adding motion to it. To be more precise, it’s a programming language that let’s you implement complex and beautiful things/design on web pages. When you notice a web page doing more than just sit there and gawk at you, you can bet that the web page is using JavaScript.

Feature of JavaScript

Scripting language and not Java: In fact, JavaScript has nothing to do with Java. Then why is it called “Java” Script? When JavaScript was first released it was called Mocha, it was later renamed to LiveScript and then to JavaScript when Netscape (founded JavaScript) and Sun did a license agreement. Object-based scripting language which supports polymorphism, encapsulation and to some extent inheritance as well.**Interpreted language: **It doesn’t have to be compiled like Java and C which require a compiler.JavaScript runs in a browser: You can run it on Google Chrome, Internet Explorer, Safari, etc. JavaScript can execute not only in the browser but also on the server and any device which has a JavaScript Engine.

What is JavaScript – Stackoverflow stats

Currently, we have 100s of programming languages and every day new languages are being created. Among these are few powerful languages that bring about big changes in the market and JavaScript is one of them.

JavaScript has always been on the list of popular programming languages. According to StackOverflow, for the 6th year in a row, JavaScript has remained the most popular and commonly used programming language.

What can JavaScript do?

JavaScript is mainly known for creating beautiful web pages & applications. An example of this is Google Maps. If you want to explore a specific map, all you have to do is click and drag with the mouse. And what sort of language could do that? You guessed it! It’s JavaScript.JavaScript can also be used in smart watches. An example of this is the popular smartwatch maker called Pebble. Pebble has created Pebble.js which is a small JavaScript Framework that allows a developer to create an application for the Pebble line of watches in JavaScript.

What is JavaScript – Applications of JavaScript
Most popular websites like Google, Facebook, Netflix, Amazon, etc make use of JavaScript to build their websites.Among things like mobile applications, digital art, web servers and server applications, JavaScript is also used to make Games. A lot of developers are building small-scale games and apps using JavaScript.## JavaScript Frameworks

One major reason for the popularity of JavaScript is the JavaScript Frameworks. Here’s a brief introduction of the most trending JavaScript frameworks :

  1. AngularJS is Google’s web development framework which provides a set of modern development and design features for rapid application development.

  2. ReactJS is another top JavaScript framework mainly maintained by Facebook and it’s behind the User Interface of Facebook and Instagram, showing off its efficiency in maintaining such high traffic applications.

What is JavaScript – JavaScript Frameworks

  1. MeteorJS is mainly used for providing back-end development. Using JavaScript on the back-end to save time and build expertise is one of the major ideas behind Meteor.

  2. jQuery can be used when you want to extend your website and make it more interactive. Companies like Google, WordPress and IBM rely on jQuery.

The Big Picture: HTML, CSS & JavaScript

Anyone familiar with JavaScript knows that it has something to do with HTML and CSS. But what is the relationship between these three? Let me explain this with an analogy.

What is JavaScript – HTML, CSS and JavaScript

Think of HTML (HyperText Markup Language) as the skeleton of the web. It is used for displaying the web.

On the other hand, CSS is like our clothes. We put on fashionable clothes to look better. Similarly, the web is quite stylish as well. It uses CSS which stands for Cascading Style Sheets for styling purpose.

Then there is JavaScript which puts life into a web page. Just like how kids move around using the skateboard, the web also motions with the help of JavaScript.

Benefits of JavaScript

There has to be a reason why so many developers love working on JavaScript. Well, there are several benefits of using JavaScript for developing web applications, here’s a few benefits:

It’s easy to learn and simple to implement. It is a weak-type programming language unlike the strong-type programming languages like Java and C++, which have strict rules for coding.

It’s all about being fast in today’s world and since JavaScript is mainly a client-side programming language, it is very fast because any code can run immediately instead of having to contact the server and wait for an answer.

Rich set of frameworks like AngularJS, ReactJS are used to build web applications and perform different tasks.

**Builds interactive websites: **We all get attracted to beautifully designed websites and JavaScript is the reason behind such attractive websites and applications.

JavaScript is an interpreted language that does not require a compiler because the web interprets JavaScript. All you need is a browser like Google Chrome or Internet Explorer and you can do all sorts of stuff in the browser.

JavaScript is platform independent and it is supported by all major browsers like Internet Explorer, Google Chrome, Mozilla Firefox, Safari, etc.

JavaScript Fundamentals

In this What is JavaScript blog, we’ll cover the following basic fundamentals of JavaScript
VariablesConstantsData TypesObjectsArraysFunctionsConditional statementsLoopsSwitch case## Variables

Variable is a name given to a memory location which acts as a container for storing data temporarily. They are nothing but reserved memory locations to store values.

What is JavaScript – Variables

To declare a variable in JavaScript use the ‘let’ keyword. For example:

let age;
age=22;

In the above example, I’ve declared a variable ‘age’ by using the ‘let’ keyword and then I’ve stored a value (22) in it. So here a memory location is assigned to the ‘age’ variable and it contains a value i.e. ’22’.

Constants

Constants are fixed values that don’t change during execution time.

To declare a constant in JavaScript use the ‘const’ keyword. For example:

const mybirthday;
mybirthday='3rd August'; 

Data types

You can assign different types of values to a variable such as a number or a string. In JavaScript, there are two categories of data types :

What is JavaScript – Data Types

Objects

An object is a standalone entity with properties and types and it is a lot like an object in real life. For example, consider a girl, whose name is Emily, age is 22 and eye-color is brown. In this example the object is the girl and her name, age and eye-color are her properties.

What is JavaScript – Objects example

Objects are variables too, but they contain many values, so instead of declaring different variables for each property, you can declare an object which stores all these properties.

To declare an object in JavaScript use the ‘let’ keyword and make sure to use curly brackets in such a way that all property-value pairs are defined within the curly brackets. For example:

let girl= {
name: 'Emily',
age: 22,
eyeColour: 'Brown'
};

In the above example, I’ve declared an object called ‘girl’ and it has 3 properties (name, age, eye colour) with values (Emily, 22, Brown).

Arrays

An array is a data structure that contains a list of elements which store multiple values in a single variable.

For example, let’s consider a scenario where you went shopping to buy art supplies. The list of items you bought can be put into an array.

What is JavaScript – Arrays example

To declare an array in JavaScript use the ‘let’ keyword with square brackets and all the array elements must be enclosed within them. For example:

let shopping=[];
shopping=['paintBrush','sprayPaint','waterColours','canvas'];

In the above example I’ve declared an array called ‘shopping’ and I’ve added four elements in it.

Also, array elements are numbered from zero. For example this is how you access the first array element:

shopping[0];		

Functions

A function is a block of organised, reusable code that is used to perform single, related action.

Let’s create a function that calculates the product of two numbers.

To declare a function in JavaScript use the ‘function’ keyword. For example:

function product(a, b) {
return a*b;
}

In the above example, I’ve declared a function called ‘product’ and I’ve passed 2 parameters to this function, ‘a’ and ‘b’ which are variables whose product is returned by this function. Now, in order to call a function and pass a value to these parameters you’ll have to follow the below syntax:

product(8,2);

In the above code snippet I’m calling the product function with a set of values (8 & 2). These are values of the variables ‘a’ and ‘b’ and they’re called as arguments to the function.

Conditional statements – if

Conditional statement is a set of rules performed if a certain condition is met. The ‘if’ statement is used to execute a block of code, only if the condition specified holds true.

What is JavaScript – if flowchart

To declare an if statement in JavaScript use the ‘if’ keyword. The syntax is:

if(condition) {
statement;
}

Now let’s look at an example:

let numbers=[1,2,1,2,3,2,3,1];
if(numbers[0]==numbers[2]) {
console.log('Correct!');
}

In the above example I’ve defined an array of numbers and then I’ve defined an if block. Within this block is a condition and a statement. The condition is ‘(numbers[0]==numbers[2])’ and the statement is ‘console.log(‘Correct!’)’. If the condition is met, only then the statement will be executed.

Conditional statements- Else if

Else statement is used to execute a block of code if the same condition is false.

What is JavaScript – Else-if flowchart

The syntax is:

if(condition) {
statement a;
}
else (condition) {
statement b;
}

Now let’s look at an example:

let numbers=[1,2,1,2,3,2,3,1];
if(numbers[0]==numbers[4] {
console.log("Correct!");
}
else {
console.log("Wrong, please try again");
}

In the above example, I’ve defined an if block as well as an else block. So if the conditions within the if block holds false then the else block gets executed. Try this for yourself and see what you get!

**Loops **

Loops are used to repeat a specific block until some end condition is met. There are three categories of loops in JavaScript :

  1. while loop
  2. do while loop
  3. for loop
While loop

While the condition is true, the code within the loop is executed.

What is JavaScript – while loop flowchart

The syntax is:

while(condition) {
loop code;
}

Now let’s look at an example:

let i=0;
while(i < 5) {
console.log("The number is " +i);
i++;
}

In the above example, I’ve defined a while loop wherein I’ve set a condition. As long as the condition holds true, the while loop is executed. Try this for yourself and see what you get!

Do while loop

This loop will first execute the code, then check the condition and while the condition holds true, execute repeatedly.

What is JavaScript – Do while loop flowchart

Refer the syntax to better understand it:

do {
loop code;
} while(condition);

This loop executes the code block once before checking if the condition is true, then it will repeat the loop as long as the condition holds true.

Now let’s look at an example:

do {
console.log("The number is " +i);
i++;
}
while(i > 5);

The above code is similar to the while loop code except, the code block within the do loop is first executed and only then the condition within the while loop is checked. If the condition holds true then the do loop is executed again.

For loop

The for loop repeatedly executes the loop code while a given condition is TRUE. It tests the condition before executing the loop body.

What is JavaScript – for loop flowchart

The syntax is:

for(begin; condition; step) {
loop code;
}

In the above syntax:

  • begin statement is executed one time before the execution of the loop code
  • condition defines the condition for executing the loop code
  • step statement is executed every time after the code block has been executed

For example:

for (i=0;i<5;i++) {
console.log("The number is " +i);
}

In the above example, I’ve defined a for loop within which I’ve defined the begin, condition and step statements. The begin statement is that ‘i=0’. After executing the begin statement the code within the for loop is executed one time. Next, the condition is checked, if ‘i<5’ then, the code within the loop is executed. After this, the last step statement (i++) is executed. Try this and see what you get!

Switch Case

The switch statement is used to perform different actions based on different conditions.

What is JavaScript – Switch case flowchart

Let’s look at the syntax for switch case:

switch(expression) {
case 1:
code block 1
break;
case 2:
code block 2
break;
default:
code block 3
break;
}

How does it work?

  • Switch expression gets evaluated once
  • Value of the expression is compared with the values of each case
  • If there is a match, the associated block of code is executed

Let’s try this with an example:

let games='football';
switch(games) {
case "throwball":
console.log("I dislike throwball!");
break;
case "football":
console.log("I love football!");
break;
case "cricket":
console.log("I'm a huge cricket fan!");
break;
default:
console.log("I like other games");
break;
}

In the above example the switch expression is ‘games’ and the value of games is ‘football’. The value of ‘games’ is compared with the value of each case. In this example it is compared to ‘throwball’, ‘cricket’ and ‘football’. The value of ‘games’ matches with the case ‘football’, therefore the code within the ‘football’ case is executed. Try this for yourself and see what you get!

With this, we come to the end of this blog. I hope you found this blog informative and I hope you have a basic understanding of JavaScript. In my next blog on JavaScript I’ll be covering in-depth concepts, so stay tuned.

Also, check out our video on JavaScript Fundamentals if you want to get started as soon as possible and don’t forget to leave a comment if you have any doubt and also, let us know whether you’d want us to create more content on JavaScript. We are listening!

Learn JavaScript in 60 Minutes | JavaScript Crash Course | JavaScript Tutorial |

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JavaScript | How to use classes in JavaScript

JavaScript | How to use classes in JavaScript

Classes in JavaScript are a special syntax for its prototypical inheritance model that resembles class based inheritance in other object oriented languages. Classes are just special functions that can be declared to resembles classes in other languages. In JavaScript, we can have class declarations and class expressions, because they are just functions. So like all other functions, there are function declarations and function expressions. Classes serve a templates to create new objects.

Defining Classes

To declare a class, or make a class declaration, we use the class keyword to do so. For example, to declare a simple class, we can write:

class Person{
  constructor(firstName, lastName) {
    this.firstName= firstName;
    this.lastName = lastName;
  }
}

Class declarations aren’t hoisted so they can used before they are defined in the code, as the JavaScript interpreter will not automatically pull them up to the top. So the class above won’t work before it’s defined in the code like the following:

const person = new Person('John', 'Smith');
class Person{
  constructor(firstName, lastName) {
    this.firstName = firstName;
    this.lastName = lastName;
  }
}

We will get a ReferenceError if we run the code above.

We can also define a class by a class expression, which is an alternative syntax for defining a class. They can be named or unnamed. We can also assign a class to a variable like we do with functions. If we do that, we can reference the class by its name. For example, we can define:

let Person = class {
  constructor(firstName, lastName) {
    this.firstName = firstName;
    this.lastName = lastName;
  }
}

To get the name of the unnamed classes above, we can get the name with the name property, like so:

console.log(Person.name);


We can also undefined a named class like the following:


let Person = class Person2{
  constructor(firstName, lastName) {
    this.firstName = firstName;
    this.lastName = lastName;
  }
}

Then to get the name of the class, we can use the name property again. So we if we write:

console.log(Person.name)


we get Person2 logged.

The class body is defined with curly brackets. We define the class members inside the brackets. The body of the class is executed in strict mode, so everything defined in strict mode applies to the definition of a class, so we can’t define variables with out some keyword before it like var , let or const , and many other rules apply when you define a class. Classes in JavaScript also have a constructor method that lets us set fields when the object is instantiated with a class . Each class can only have one constructor method in it. If there’s more than one, then SyntaxError will be thrown. A constructor have to also call the super method to call the constructor of the super class inside if it the class extends a parent class.

Methods that aren’t declared static constitutes of the prototypical methods of the class. They are called after an object has been created by using the new keyword. For example, the following class have only prototypical methods:


class Person{
  constructor(firstName, lastName) {
    this.firstName = firstName;
    this.lastName = lastName;
  }
  get fullName(){
    return `${this.firstName} ${this.lastName}`  
  }
  sayHi(){
    return `Hi, ${this.firstName} ${this.lastName}`
  }
}

In the Person class above, fullName and sayHi are prototypical methods. They are called like this:

const person = new Person('Jane', 'Smith');
person.fullName() // 'Jane Smith'

Static methods are methods that can be called without creating an object from the class using the new keyword. For instance, we can have something like the following:


class Person {
  constructor(firstName, lastName) {
    this.firstName = firstName;
    this.lastName = lastName;
  }
  get fullName() {
    return `${this.firstName} ${this.lastName}`
  }
  sayHi() {
    return `Hi, ${this.firstName} ${this.lastName}`
  }
  static personCount() {
    return 3;
  }
}

We can call the personCount function without using the new keyword to create an instance of the class. So if we write:

Person.personCount

We get 3 returned.

The this value inside prototypical methods will be the value of the object. For static methods the value of this has the class that the static method is in as the value.

Getters and Setters

JavaScript classes can have getters and setter functions. Getters, as the name suggests, is a method that lets us get some data from a class. Setters are methods that gives us the ability to set some fields of the class. We denote getter functions with the get keyword and setters with the set keyword. For example, we can write a class that has getters and setters like the following:

class Person {
  constructor(firstName, lastName) {
    this._firstName = firstName;
    this._lastName = lastName;
  }
  get fullName() {
    return `${this.firstName} ${this.lastName}`
  }
  get firstName() {
    return this._firstName
  }
  get lastName() {
    return this._lastName
  }
  sayHi() {
    return `Hi, ${this.firstName} ${this.lastName}`
  }
  set firstName(firstName) {
    this._firstName = firstName;
  }
  set lastName(lastName) {
    this._lastName = lastName;
  }
}

Then when we use the new keyword to construct a Person object, we can use them in the following way:


const person = new Person('Jane', 'Smith');
person.firstName = 'John';
person.lastName = 'Doe';
console.log(person.firstName, person.lastName)

Since we have the getter and setter functions, we can use them to set the data directly to set the data for firstName and lastName of the Person class. In the setter functions, which start with the keyword set , what we assign to them get passed into the parameters and set in the member of the class. In the getter functions, which are denote by get we return the member values so that we can use them.

JavaScript Inheritance

In JavaScript, we can create classes where the properties can be included in the properties of a child class.

So, we can have a high-level class that contains the properties that are common to all the child classes, and the child class can have its own special properties that are not in any other classes.

For example, if we have an Animal class with the common properties and methods, like name and the eat method, then the Bird class can just inherit the common properties in the Animal class. They don’t have to be defined in the Bird class again.

We can write the following to do inheritance in JavaScript:

class Animal {
  constructor(name) {
    this.name = name;
  }
  eat() {
    console.log('eat');
  }
}
class Bird extends Animal {
  constructor(name, numWings) {
    super(name);
    this.numWings = numWings;
  }
}
const bird = new Bird('Joe', 2);
console.log(bird.name)
bird.eat();

In the example above, we have the parent class, Animal, that has the eat method, which all classes that extends from Animal will have, so they don’t have to define eat again.

We have the Bird class which extends the Animal class. Note that in the constructor of the Bird class, we have the super() function call to call the parent’s class constructor to populate the properties of the parent class in addition to the properties of the child class.

Classes cannot extend regular objects, which cannot be constructed with the new keyword. If we want to inherit from a regular object, we have to use the Object.setPrototypeOf function to set a class to inherit from a regular object. For example:

const Animal = {
  eat() {
    console.log(`${this.name} eats`);
  }
};
class Cat{
  constructor(name) {
    this.name = name;
  }
}
class Chicken{
  constructor(name) {
    this.name = name;
  }
}
Object.setPrototypeOf(Cat.prototype, Animal);
Object.setPrototypeOf(Chicken.prototype, Animal);
let cat = new Cat('Bob');
let chicken = new Chicken('Joe');
cat.eat();
chicken.eat();

If we run the example code above, we have see Bob eats and Joe eats logged because we have inherited the eat function from the Animal object.

this Keyword

The this keyword allows us to access the current object’s properties inside an object, unless you’re using arrow functions.

As we can see from the above example, we can get the properties of the instance of the child and the parent class in the object.

Mixins

We can use mixins to do multiple inheritance in JavaScript. Mixins are templates for creating classes. We need mixins to do multiple inheritance because JavaScript classes can only inherit from one super class, so multiple inheritance isn’t possible.

For example, if we have a base class, we can define mixins to incorporate the members from multiple classes into one by composing the mixins by calling one and then pass the returned result into the next one as the argument, an so on, like so:

class Base {
  baseFn() {
    console.log('baseFn called');
  }
}
let classAMixin = Base => class extends Base {
  a() {
    console.log('classAMixin called');
  }
};
let classBMixin = Base => class extends Base {
  b() {
    console.log('classBMixin called');
  }
};
class Bar extends classAMixin(classBMixin(Base)) {}
const bar = new Bar();
bar.baseFn()
bar.a()
bar.b()

In the code above, we have the Base class which we pass into the classBMixin to get the b function into the Base class, then we call the classAMixin by passing in the result of classBMixin(Base) into the argument of the classAMixin to return the a function from classAMixin into the Base class and then return the whole class with all the functions from all the classes incorporated into one.

If we call all the functions above like we did by creating an instance of the Bar object and then call the baseFn , a and b functions, then we get:

baseFn called
classAMixin called
classBMixin called

This means that we have all the functions from the mixins incorporated into the new Bar class.

In JavaScript, classes are just syntactic sugar to make the prototypical inheritance of JavaScript clearer by letting us structure the code in a way that’s more like typical inheritance class based object oriented inheritance pattern. This means that we write classes to and use the new keyword to create objects from the classes, but underneath the syntactic sugar, we are still using prototypical inheritance to extend objects. We can extend classes from objects and we can also use mixins to do multiple inheritance in of JavaScript classes.