Object Oriented Programming in JavaScript

Object Oriented Programming in JavaScript

Object-oriented programming is a high-level language where we use objects to model real-world things to represent our programs while providing a simple way to access functionality.

Object-oriented programming is a high-level language where we use objects to model real-world things to represent our programs while providing a simple way to access functionality.

Overview

In JavaScript, almost everything is referred to as an object. It is possible to create your own objects to encapsulate related functions and variables to act as containers.

It is paramount to have some familiarity with basic HTML and CSS before bracing yourself for Object-Oriented Programming in JavaScript.

Now, I would like to start you off with the basic object ‘Person’. A person, for example, has some generic data and functionality. A Person, for example, has many characteristics like; address, weight, height, shoe size, passport number, DNA profile, ID number, and many other traits.

For now, we are interested in their name, age, gender and interests. This process of creating a simple model from a complex thing is called abstraction.

Example

Class: Person
Name[firstName, secondName]
Age
Gender
Bio{‘[Name] is [Age] years old. And they like [Interests]'}
Greeting{‘Hi! I\'m [Name]'.}

From the above class, we can create object instances, a process called instantiation.

Object:person1
Name[Robert, Smith]
Age:32
Gender: Male
Interests: music, skiing
Bio{‘Robert Smith is 32 years old. He likes music and skiing.'}
Greeting{‘Hi! I\'m Robert'.}
Object: person2
Name [Diana, Hope]
Age:28
Gender: Female
Interests: boxing, brewing
Bio{‘Diana Hope is 28 years old. She likes boxing and brewing'.}
Greetings:{‘Hi! I\'m Diana'}

We now run a constructor function to create an object instance. In case we want to create a more specific group of people for example, students and teachers, we employ inheritance whereby, we create child classes from parent classes.

The child classes will define their own specialized features while reusing the common functionality to all object types.

Example

Class: Person
Name [firstName, lastName]
Age
Gender
Interests
Bio{‘[Name] is [Age] years old. They like [Interests].'}
Greeting: {‘Hi! I\'am [Name]'}
Class: Teacher
Name [firstName, lastName]
Age
Gender
Bio{‘[Name] is [Age] years old. They like [interest].'}
Subject
Greeting{‘Hello. My name is [Prefix] [lastName] and I teach [Subject]'}
Class: Student
Name [firstName, lastName]
Age
Gender
Interests
Bio{‘[Name] is [Age] years old. They like [Interests].'}
Greeting{‘Yo! I\'am [firstName]'}

In the example above, teachers and students share common features such as name, gender, and age, so we define these features once.

We define greeting in a separate class because a teacher and a student might have different ways to greet, hence defining greeting features in a separate class with a different namespace.

e.g

Student:
Greeting {‘Yo! I\'am [firstName]'}
Yo! I'm Sam
Teacher:
Greeting{‘Hello, my name is [Prefix] [lastName] and I teach [Subject]'}
Hello, my name is Mr. Griffin, and I teach Chemistry


It is possible to create object instances from child classes;

Example

Class: Teacher
Name [firstName, lastName]
Age
Interests
Bio {‘[Name] is [Age] years old. They like [Interests].'}
Subject
Greeting {‘Hello, my name is [Prefix] [lastName], and I teach [Subject].'}

Object: teacher1
Name [David, Griffin]
Age: 31 Gender:Male
Interests: football, cooking
Bio{‘David Griffin' is 31 years old. They like football and cooking.'}
Subject: Math
Greeting{‘Hello my name is Mr. Griffin, and I teach Math.'} Object: teacher2
Name [Melanie, Hall]
Age: 26 Gender: Female
Interests: playing guitar, archery
Bio{‘Melanie Hall is 26 years old. They like playing guitar and archery.'}
Subject: Physics
Greeting{‘Hello my name is Ms. Hall and I teach Physics.'}

Now let me shift gears to how this OOP theory can be applied to JavaScript. JavaScript uses special functions namely constructor functions, to define and initialize objects and their features.

We create objects using constructors when we are not sure how many objects to create.

I will now explore how to create classes via constructors and creating instances from them in JavaScript. First, we need to create HTML in our example, that done, we add script elements into it.

Example

Function createNewPerson(name) {
var obj = {};
obj.name= name;
obj.greeting = function(){
alert(‘Hi! I\'m' + obj.name + ‘.');
};
Return obj;
}

Now, we can create a new person by calling this function;

var Silva = createNewPerson (‘Silva')
Silva.name
Silva.greeting();
Instead of creating empty objects, make use of constructor functions, they are handy.
Function Person(name) {
this.name = name;
this.greeting = function() {
alert(‘ Hi! I\'m ' + this.name + ‘.')
}

Note that the constructor function is JavaScript’s version of a class. A constructor has all features you expect to see in a function, though it doesn’t return anything.

It only defines properties and methods using this keyword. This means, whenever we create the object instance, the object name property will be equal to the name passed to the constructor called and thegreeting() method will use the name-value passed to the constructor call. Now we call the constructor to create objects. Example

var person1 = new Person(‘Robert'); var person2 = new Person(‘Sara');

Now, add the following code to JSConsole;

person1.name
person1.greeting()
person2.name
person2.greeting()

The above code creates two new objects stored under a different namespace. Their functionality is packaged in a way it won’t clash with other functionality. This is used to ensure created objects use their own values.

Example

function person (name) {
this.name = name;
this.greeting = function() {
alert(‘Hi! I\'m' + this.name + ‘.');
};
}

Now, person1 and person2 variables contain objects as follows;

{
name: ‘Robert',
greeting: function() {
alert(‘Hi! I\'m' + this.name + ‘.');
}
}

{
name: ‘Sara',
greeting: function() {
alert(‘Hi! I\'m' + this.name + ‘.');
}
}

Finished Constructor

Here is a complete constructor for you toperson() study. It seems a bit complex but it is the same constructor we used before.

Example

Function Person(first, last, age, gender, interests) {
this.name = {
first: first;
last: last;
};

this.age= age;
this.gender = gender;
this.interests = interests
this.bio = function() {
alert(this.name.first + ‘ ' + this.name.last + ‘is' + this.age + ‘years old. He likes' + this.Interests[0] + ‘and' + this.interests[1] + ‘.' );
};
}

To create an object instance from the above, we use:

var person1 = new Person(‘Robert', ‘Smith', 32, ‘male' [‘music','skiing']) ;

Now access the properties and methods;

Person1[‘Age']
Person1.interests
Person1.bio()

Other ways to create object instances

Apart from declaring an object literal and using constructor function, there are other ways of creating object instances.

The <strong>object()</strong> constructor

Use a object()constructor to create a new object as follows;

var Person1 = new Object();

The above object constructor stores empty objects in Person1 variable, then add objects using dot or bracket notations. For example;

Person1.name='Christo';
Person1[Age] = 38;
Person1.greeting = function() {
Alert(‘Hi! I\'m' + this.name + ‘.')
};

Also, pass an object literal to theobject() constructor as a parameter to pre-fill it with properties and methods.

var Person1 = new Object({
name: ‘Christo';
age: 38;
greeting: function()
alert(‘Hi! I\'m' + this.name + ‘.');
}
});

The <strong>Create()</strong> method

This is a built-in method in JavaScript where you can create new objects based on an existing object. Its only limitation is, it cannot be supported by old browsers.

var Person2 = object.Create(Person1);

Now create Person2 using Person1.

person2.name;
person2.greeting()

conclusion

Up until now, we have explored JavaScript object-oriented theory in-depth, you now have a clue of what you can achieve with OOPJS. I will only direct you to explore more on MDN

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JavaScript developers should you be using Web Workers?

JavaScript developers should you be using Web Workers?

Do you think JavaScript developers should be making more use of Web Workers to shift execution off of the main thread?

Originally published by David Gilbertson at https://medium.com

So, Web Workers. Those wonderful little critters that allow us to execute JavaScript off the main thread.

Also known as “no, you’re thinking of Service Workers”.

Photo by Caleb Jones on Unsplash

Before I get into the meat of the article, please sit for a lesson in how computers work:

Understood? Good.

For the red/green colourblind, let me explain. While a CPU is doing one thing, it can’t be doing another thing, which means you can’t sort a big array while a user scrolls the screen.

This is bad, if you have a big array and users with fingers.

Enter, Web Workers. These split open the atomic concept of a ‘CPU’ and allow us to think in terms of threads. We can use one thread to handle user-facing work like touch events and rendering the UI, and different threads to carry out all other work.

Check that out, the main thread is green the whole way through, ready to receive and respond to the gentle caress of a user.

You’re excited (I can tell), if we only have UI code on the main thread and all other code can go in a worker, things are going to be amazing (said the way Oprah would say it).

But cool your jets for just a moment, because websites are mostly about the UI — it’s why we have screens. And a lot of a user’s interactions with your site will be tapping on the screen, waiting for a response, reading, tapping, looking, reading, and so on.

So we can’t just say “here’s some JS that takes 20ms to run, chuck it on a thread”, we must think about where that execution time exists in the user’s world of tap, read, look, read, tap…

I like to boil this down to one specific question:

Is the user waiting anyway?

Imagine we have created some sort of git-repository-hosting website that shows all sorts of things about a repository. We have a cool feature called ‘issues’. A user can even click an ‘issues’ tab in our website to see a list of all issues relating to the repository. Groundbreaking!

When our users click this issues tab, the site is going to fetch the issue data, process it in some way — perhaps sort, or format dates, or work out which icon to show — then render the UI.

Inside the user’s computer, that’ll look exactly like this.

Look at that processing stage, locking up the main thread even though it has nothing to do with the UI! That’s terrible, in theory.

But think about what the human is actually doing at this point. They’re waiting for the common trio of network/process/render; just sittin’ around with less to do than the Bolivian Navy.

Because we care about our users, we show a loading indicator to let them know we’ve received their request and are working on it — putting the human in a ‘waiting’ state. Let’s add that to the diagram.

Now that we have a human in the picture, we can mix in a Web Worker and think about the impact it will have on their life:

Hmmm.

First thing to note is that we’re not doing anything in parallel. We need the data from the network before we process it, and we need to process the data before we can render the UI. The elapsed time doesn’t change.

(BTW, the time involved in moving data to a Web Worker and back is negligible: 1ms per 100 KB is a decent rule of thumb.)

So we can move work off the main thread and have a page that is responsive during that time, but to what end? If our user is sitting there looking at a spinner for 600ms, have we enriched their experience by having a responsive screen for the middle third?

No.

I’ve fudged these diagrams a little bit to make them the gorgeous specimens of graphic design that they are, but they’re not really to scale.

When responding to a user request, you’ll find that the network and DOM-manipulating part of any given task take much, much longer than the pure-JS data processing part.

I saw an article recently making the case that updating a Redux store was a good candidate for Web Workers because it’s not UI work (and non-UI work doesn’t belong on the main thread).

Chucking the data processing over to a worker thread sounds sensible, but the idea struck me as a little, umm, academic.

First, let’s split instances of ‘updating a store’ into two categories:

  1. Updating a store in response to a user interaction, then updating the UI in response to the data change
  2. Not that first one

If the first scenario, a user taps a button on the screen — perhaps to change the sort order of a list. The store updates, and this results in a re-rendering of the DOM (since that’s the point of a store).

Let me just delete one thing from the previous diagram:

In my experience, it is rare that the store-updating step goes beyond a few dozen milliseconds, and is generally followed by ten times that in DOM updating, layout, and paint. If I’ve got a site that’s taking longer than this, I’d be asking questions about why I have so much data in the browser and so much DOM, rather than on which thread I should do my processing.

So the question we’re faced with is the same one from above: the user tapped something on the screen, we’re going to work on that request for hopefully less than a second, why would we want to make the screen responsive during that time?

OK what about the second scenario, where a store update isn’t in response to a user interaction? Performing an auto-save, for example — there’s nothing more annoying than an app becoming unresponsive doing something you didn’t ask it to do.

Actually there’s heaps of things more annoying than that. Teens, for example.

Anyhoo, if you’re doing an auto-save and taking 100ms to process data client-side before sending it off to a server, then you should absolutely use a Web Worker.

In fact, any ‘background’ task that the user hasn’t asked for, or isn’t waiting for, is a good candidate for moving to a Web Worker.

The matter of value

Complexity is expensive, and implementing Web Workers ain’t cheap.

If you’re using a bundler — and you are — you’ll have a lot of reading to do, and probably npm packages to install. If you’ve got a create-react-app app, prepare to eject (and put aside two days twice a year to update 30 different packages when the next version of Babel/Redux/React/ESLint comes out).

Also, if you want to share anything fancier than plain data between a worker and the main thread you’ve got some more reading to do (comlink is your friend).

What I’m getting at is this: if the benefit is real, but minimal, then you’ve gotta ask if there’s something else you could spend a day or two on with a greater benefit to your users.

This thinking is true of everything, of course, but I’ve found that Web Workers have a particularly poor benefit-to-effort ratio.

Hey David, why you hate Web Workers so bad?

Good question.

This is a doweling jig:

I own a doweling jig. I love my doweling jig. If I need to drill a hole into the end of a piece of wood and ensure that it’s perfectly perpendicular to the surface, I use my doweling jig.

But I don’t use it to eat breakfast. For that I use a spoon.

Four years ago I was working on some fancy animations. They looked slick on a fast device, but janky on a slow one. So I wrote fireball-js, which executes a rudimentary performance benchmark on the user’s device and returns a score, allowing me to run my animations only on devices that would render them smoothly.

Where’s the best spot to run some CPU intensive code that the user didn’t request? On a different thread, of course. A Web Worker was the correct tool for the job.

Fast forward to 2019 and you’ll find me writing a routing algorithm for a mapping application. This requires parsing a big fat GeoJSON map into a collection of nodes and edges, to be used when a user asks for directions. The processing isn’t in response to a user request and the user isn’t waiting on it. And so, a Web Worker is the correct tool for the job.

It was only when doing this that it dawned on me: in the intervening quartet of years, I have seen exactly zero other instances where Web Workers would have improved the user experience.

Contrast this with a recent resurgence in Web Worker wonderment, and combine that contrast with the fact that I couldn’t think of anything else to write about, then concatenate that combined contrast with my contrarian character and you’ve got yourself a blog post telling you that maybe Web Workers are a teeny-tiny bit overhyped.

Thanks for reading

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Further reading

An Introduction to Web Workers

JavaScript Web Workers: A Beginner’s Guide

Using Web Workers to Real-time Processing

How to use Web Workers in Angular app

Using Web Workers with Angular CLI