All language subtitles for 2. What is Node.js 2

So let's dive into the most important question, what is nodejs?

Nodejs is a javascript runtime

and now what does this mean?

You know javascript, it's a programming language you typically use in the browser to manipulate your dom,

to manipulate the page which was loaded in the browser,

for example to open a popup, a modal or add any kinds of effects because Javascript is a language that

runs in the browser that allows you to interact with the page after it was loaded and it therefore is a

crucial part when it comes to building interactive user interfaces in the browser,

so whatever your users see. However javascript is not limited to that.

Nodejs is a different version of javascript you could say, it is basically built on javascript, it adds

some features to it, is not capable of doing some other things you can do with javascript in the browser,

so it basically takes javascript and puts it into a different environment.

It allows you to run javascript code on the server

you could say, in theory not just on the server but on any machine though.

So it basically allows you to run javascript not just in the browser but anywhere else like a normal

programming language, like normal programs on your computer or some computer in the Internet effectively

making it a great choice for building web applications that run on servers which are just computers

running somewhere in the Internet.

So in detail, this means that we can use nodejs to run javascript outside of the browser,

that is the core takeaway,

now how does this work

technically? Well nodejs uses v8 and v8 simply is the name of the javascript engine built by Google

that runs javascript in the browser,

so back to the browser we now are. V8 is simply the name the creators gave their engine

and what does an engine mean?

Well it simply means that engine takes javascript code, the code running in your browser then or in node's

case which builds up on v8,

also the nodejs javascript code, it takes that javascript code and compiles it to machine code

and this is what your browser does too, what v8 does in your browser.

It does take your javascript code and compile it to machine code because that is the code that runs ultimately

on your computer

and that can be handled efficiently.

Now this is done by v8, v8 itself is written in C++ but that doesn't really matter too

much for you,

you don't need to write any C++ code to use javascript or nodejs

but nodejs

basically takes that v8 codebase which is written in C++ and adds certain features like for example

working with your local file system, opening files, reading files, deleting files,

these are all things which are not possible in the browser,

you can't access your local filesystem in the browser for security reasons, so this is not supported.

Nodejs adds these features to v8's engine you could say

so that you can suddenly do that. Now

nodejs does not run in the browser so these restrictions still apply,

there you use vanilla

v8, so v8 only without the nodejs extensions

but if you then install nodejs, you can use it to basically use that extended v8 version

to run javascript scripts on your computer which then suddenly can access these new features because they

don't run in the browser but are directly executed through that nodejs runtime you could say.

So this is how that works together and what nodejs does. It allows you to run javascript on your computer

and it adds useful functionalities to the javascript engine so that you can do more useful stuff there

than you can do with browser side javascript.

Now one important note maybe on this point

also is that of course some features are also taken away. In the browser you use javascript to interact

with the document object model,

so with the html elements on your page,

if you just execute a javascript file directly, you of course have no attached page and therefore these

features are missing. But this is a lot of theory,

why don't we just have a look at this and see how we can install and use nodejs and what it actually

does for us.

Let's do that in the next lecture.