Understanding Node

• As an asynchronous event-driven JavaScript runtime, Node.js is designed to build scalable network applications. Upon each connection, the callback is fired, but if there is no work to be done, Node.js will sleep. Furthermore, users of Node.js are free from worries of dead-locking the process, since there are no locks. Almost no function in Node.js directly performs I/O, so the process never blocks
• More about node is here.

Download and install node

• download and install latest version for your OS from here
• check if node is installed by running command node -v on your terminal
• above command will print veriosn of node if node istalled.

% node -v
v10.21.0

Why is Javascript is Node's language?

• Syntax is same for frontend and backend
• Shared code and data structures between frontend and backend
  • shared libraries such as underscore, encryption lib
  • custom algorithm and logic for funtions
  • data structure and object definitions

The benefits and features of Javascript

• Frontend and backend share the language
• Frontend and backend share the code
• Dynamic language - this means type is determined by the value , not when variabe is declared
• JSON comes naturally with Javascript

Asynchrounous tasks and callbacks

• When you execute a task synchronously, you wait for it to finish before moving on to another task which is what causes blocking.
• On the other hand, when you execute tasks asynchronously, you can move on to another task without having to wait for the previous task to finish
• The most common way to get started with asynchronous code is to do callbacks. So let's take a look at some code.

• What if we end up installing several third party packages, and we want to keep track of what we have installed and are dependent on in a list somewhere? That's where the "package.json" file comes in.
• run npm init command to initiate npm in project repo.

• What is a framework? It's sometimes interesting when we look at a definition in its generic form. For example, a framework is an essential supporting structure of a building, vehicle, or object.
• And in software, it's essentially the same thing. It is a supporting structure that allows you to build on top of it. When it comes to web, and we want to build large APIs, or maybe HTTP servers, we can leverage web frameworks, and there are several options we can look at.
• Each of these provide us with the structure and components you need to quickly make serving static files, like traditional websites, easy. Or we can put together a web API to interact in a web app. A web API is a service that allows us to get and save data to our server or back end, such as a web API that allows us to maybe create users, serve a list of users, etc.

Static serving with Express

• You can either host static content or dynamic content.
• Static content can be things like HTML files for web sites or images, videos, etc.
• Dynamic content, on the other hand, is served through a web API, or sometimes it's used to serve dynamic webpages where the content or the view is composed on the server itself.

Creating browser app

Create a get messages service

Create a post messages service

Connect to Socket.io from the browser app

• With Socket.IO, we will be able to notify clients or the app running in the browser when another user has sent a chat message, that way the app will update their message list instantly.
• Socket.IO works as pushing notification work.
• The nice thing about the Socket.IO library is that if a browser is older and does not support WebSockets, it will default back to polling and it has that functionality built in so it will always work, even if it's not as efficient with older browsers.

Create your Socket.io event

Sample Code above steps is here

• There are many different database technologies, such as MongoDB, MySQL, Veras, and many more. Node has packages to work with most of these options.
• Most of these options fall into two categories: Either SQL or NoSQL.

• The key word here is structured, meaning the data stored inside is structured.
• The database knows and cares about the structure, and the tables that store the data must be designed with that in mind.
• The object classes, which represent the items that will go into those structured tables, must also be designed. There is a lot of up-front design work in doing so, but also some performance and query benefits in some cases.

• We just put data into collections without paying much attention to the structure. As a result, there's less up-front design work, and possible performance increases in some cases.

• Mongoose allows us to elegantly work with our mongodb database with object schemas.
• Object schemas are JavaScript objects we create that will represent the type of data we will be putting in our database.
• Even though mongodb is NoSQL, and does not have structure, with Mongoose, there is a bit of structure we must design initially.
• This gives us some benefits of easily interacting with our data through objects, and other things such as validation.