Original subtitles

Almost everyone that has worked with JavaScript has heard of the V8 engine.

The idea of the JavaScript engine, and most people know that JavaScript is a single threaded language,

that it uses a callback.

You may also hear phrases like JavaScript is an interpreted language.

Let's tackle what that means over the next couple of videos.

What is this engine that we speak of?

Well, if I write some code like, let's say cost is happy equals to true.

Well, we just wrote some JavaScript.

I'm assigning the true boolean to the variable is happy.

Now how do we read this or how does the computer read this?

Imagine if somebody comes up to you and gives you a computer and they tell you, hey, tell this computer

to display a picture of horses on the screen.

And you start looking at this computer and you tell the computer to display an image of a horse or horses

in French.

Is the computer going to understand you?

No.

The computer would have no idea what you just said.

In similar fashion, if I gave a computer with a CPU.

A file that is a JavaScript file.

And I tell it, hey, read this file and do something for me.

Well, the computer only understands ones and zeros at the end of the day.

And when we give it the JavaScript file, it's like me talking to a computer in French and the computer

being like, What?

What are you talking about?

Plus, talking to a computer in French while people are going to look at you like you're a crazy person.

So the computer doesn't really know what JavaScript is.

So how are we able to communicate using a JavaScript file so that the computer displays pictures of

horses?

And this is the first step in our learning, and that is the JavaScript engine.

By having a JavaScript engine right over here, it allows you to give this machine the JavaScript file,

and this machine is going to understand this file and tell the computer what to do to display pictures

of horses.

In a sense, you just created a translator so you can communicate with somebody that doesn't know your

language.

And this special engine called the JavaScript engine understands JavaScript.

Our computer finally understands us because of this JavaScript engine and it says, I'm on it, boss.

I'll start displaying those horse pictures.

There you go.

That's our first step.

And over the next couple of videos, we're going to talk about exactly what's happening inside.

But do you think there's one JavaScript engine or many JavaScript engines?

Well, as you can see from this Wikipedia list, there are a ton of engines and they're called xma script

engines.

And we'll get into why that is later.

But these are all the JavaScript engines, some of them you may have heard of like V8 or spider monkey

or chakra.

So any time we use an engine, we're able to give it a JavaScript file.

And this JavaScript file gets understood by the engine, and it allows this engine to communicate and

tell the machine, the computer, to do what we ask it to do with JavaScript.

Now these engines are written by programmers.

For example, V8 engine is written in C++.

But why do people write these engines?

2008 marked a really pivotal moment in history when it comes to JavaScript because V8 was released by

Google.

Before then, most browsers used engines that were very basic, which meant that JavaScript was a little

bit slow.

You see, Google had this problem.

They had something called Google Maps.

And Google Maps, as you know, requires a lot of power.

It does a lot of things.

You can ask for directions to zoom in and zoom out, maybe even use Street View and all the previous

engines before it would make Google Maps very, very slow on the browser.

And Google, because they're a search engine, they want everybody to use their search engine and they

built a browser in order for them to control more of the market.

So with Google Maps and their own Chrome browser, they said, Hmm.

We're going to write our own JavaScript engine, the V8 engine.

So that JavaScript runs way faster on the browser than it's done previously.

And in 2008 they released V eight.

But the big takeaway for us here is that really, really smart people work on these engines so that

our JavaScript runs as fast as possible on the browser, on the server or any type of computer.

So every day JavaScript gets faster and faster for us because of the work that goes into these engines.

Okay.

But what is inside this engine, this magical machine that understands JavaScript?

It reads our code and then it runs this code.

Let's get into that in the upcoming video.

Bye bye.