The Express. js Course - Module 1: Getting Started with Node. js

1. 1. Introduction to the Node.js Universe: Welcome to the Express course. My name is Shen Rogovinhi and I'm super excited to be your instructor for this course. I have done my best to create the most comprehensive and up to date express course, it shows you all the modern ways to build applications with Express. And I hope by the end of this course, you will become an expert Express developer. So are you ready to get started? Then let's jump in. 2. 2. Understanding Node.js: A Primer: Node or Node JS is an open source and cross platform runtime environment for executing JavaScript code outside of a browser. Quite often, we use node to build the backend services, also known as APIs or application programming interfaces. These services are the power source for client applications, like a web application running in a browser or a mobile application running in a mobile device. These services are nothing but what the user sees and interacts. They are just a surface. They need to talk to some kind of services sitting in the server or in the cloud to store data, send emails, push notifications, pickup workflows, and so on. Node is ideal for building highly scalable, data intensive and real time backend services that power our client applications. Now you might ask, but Shen, there are other tools and frameworks out there for building backend services such as asp.net, Rails, Jango and so on. So what's so special about node? Well, node is easy to get started and can be used for prototyping and agile development, but it can also be used for building super fast and highly scalable services. It is used in production by large companies such as PayPal, Uber, Netflix, Walmart, and so on. In fact, at PayPal, they rebuilt one of their Java and spring based application using Node, and they found that the node application was built twice as fast with fewer people, 33% fewer lines of code, and 40% fewer files. But more importantly, they double the number of requests served per second while decreasing the average response time by 35%. So node is an excellent choice for building highly scalable services. Another reason for using Node is that in node application, we use JavaScript. So if you're a front end developer and no JavaScript, you can reuse your JavaScript skills and transition to a full stack developer and get a better job with a better pay. You don't have to learn a new programming language. Also, because you can use JavaScript both on the front end and back end, your source code will be cleaner and consistent. You will use the same naming convention, same tools, and the same best practices. And finally, another reason for using Node is that it has the largest ecosystem of open source libraries available to you. So for pretty much any features or building blocks you want to add to your application, there is some open source library out there that you can use. So you don't have to build any building blocks from scratch, and instead, you can focus on the core of your application. Next, we are going to look at the architecture of node. 3. 3. The Blueprint of Node.js Architecture: In the last video, we learned that node is a rundom environment for executing JavaScript code. But what is a rundom environment really? Well, before node, we use JavaScript only to build web applications that run inside of a browser. So every browser out there has what we call a JavaScript engine that takes a JavaScript code and converts it to a code that a computer can understand. For example, Microsoft Edge uses Chaka, Firefox uses Spider Monkey. In Chrome uses eight. And because of these varieties of engines, at sometimes JavaScript code can behave differently in one browser for another. Now a browser provides a runtime environment for JavaScript code. For example, you probably know that in a browser, we have the window or document object. These objects allow us to work with the environment in which our code is running. Up to 2009, only way to execute JavaScript code was inside of a browser. In 2009, Ryan Dall, the creator of Node, came up with a brilliant idea. He thought that it would be great to execute JavaScript outside of a browser. So he took Google's VD engine, which is the fastest JavaScript engine out there and embedded it inside a C program and called that program Node. So similar to a browser, node is a runtime environment for JavaScript code. It contains a JavaScript engine that can execute our JavaScript code, but it also has certain objects that provide an environment for our JavaScript code. But these objects are different from the environment objects that we have in a browser. For example, we don't have the document object, instead, we have other objects that gives us more interesting capabilities. For example, we can work with a file system, listen for a request at a given port, and so on. We can do stuff like that inside of a browser, right? So in essence, node is a program that includes a weird engine plus some additional modules that gives us capabilities not available inside browsers. We can work with a file system or network, and so on. Both Chrome and node share the same JavaScript engine, but they provide different runtime environments for JavaScript. I have seen people comparing node to C sharp or Ruby or some other programming languages. But these comparisons are fundamentally wrong because node is not a programming language. It's like comparing a car with an apple. By the same token, node should not be compared with frameworks such as sp.net, Rails or jango and so on. These are frameworks for building web applications. Node is not a framework. It's a runtime environment for executing JavaScript code. Next, we are going to take a look at how node works. 4. 4. Node.js Under the Hood: Operational Mechanics: Earlier, I mentioned that node applications are highly scalable, and this is because of the non blocking or asynchronous nature of node. What I meant by asynchronous? Let me give you a metaphor. Imagine you go to a restaurant, a waiter comes to a table, takes your order, and gives it to the kitchen. Then they move on to serve another table while the chef is preparing your meal. So the same person can serve many different tables. They don't have to wait for the chef to cook one meal before they serve another table. This is what we call non blocking or asynchronous architecture, and this is how no applications work. The er is like a thread allocated to handle a request. So a single thread is used to handle multiple requests. In contrast to non blocking or asynchronous architecture, we have blocking or synchronous architecture. Let's see how that works. So back to our restaurant example. Imagine you go to another restaurant and in this restaurant, a waiter is allocated to you. It takes your order and gives it to the kitchen. Now they're sitting in the kitchen waiting for the chef to prepare your meal. At this time, they are not doing anything else. They are just waiting and not going to take order from another table until your meal is ready. This is what we call blocking or synchronous architecture, and that's how applications built with frameworks like asp.net or RAILS work out of the box. So when we receive a request from the server, a thread is allocated to handle the request. As part of handling that request, it is likely that we are going to query a database. And as you know, sometimes it may take a while until the result is ready. When the database is executing the query, that thread is sitting there waiting. It can be used to serve another client. So we need a new thread to solve another client and imagine what would happen if we have a large number of clients. At some point, we're going to run out of threads to serve the clients. The new clients have to wait until free threads are available. Or if you don't want them to wait, we need to add more hardware. So with this kind of architecture, you are not utilizing the resources efficiently. This is the problem with blocking or synchronous architecture. And as I explained, that's how applications are built with frameworks like asp.net or by defact. Of course, in asp.net, it is possible to use asynchronous architecture, but you will have to do extra work for that. In contrast, node applications are asynchronous by default, so you don't have to do anything extra. In node, we have a single thread to handle all the requests. When a request arrives, that single thread is used to handle that request. If we need to query a database, our thread doesn't have to wait for the database to return the data. While the database is executing our query, that thread will be used to solve another client. When the database prepares the result, it puts a message in what we call an event queue. Node is continuously monitoring this queue in the background. When it finds an event in this queue, it will take it out and process it. This kind of architecture makes Node idle for building applications that include a lot of disk network access. We can serve more clients without the need to throw in more hardware. And that's why node applications are highly scalable. In contrast, NO should not be used for CPU intensive applications like video encoding or an image manipulation service. In this kind of applications, we have a lot of calculations that should be done by CPU and few operations that touch the file system or the network. Since no applications are single threaded, when performing the calculations to serve one client, other clients have to weigh, and that's why NO should not be used for CPU intensive applications. Should only be used to build data intensive applications or real time applications. That's a lot of theory. Next, we will see node installation and build our first node application. 5. 5. Setting Up Your Node.js Environment: This lecture, I'm going to show you thousand store node. If you are on Windows, open up Power Shell. If you are on Mac or Linux, open up the term no. First, let's see if you are already using node on your machine or not. So run node space dash version. You can see on this machine, I'm running node version 16.16 0.0. This is an earlier version of No. The latest stable version is 18.16 0.1. Now on your machine, chances are you may not have node or you might have an earlier version. The way, I want you to install the latest version of K. So open up your browser and head over to nodjs.org. On the homepage, you can see we have two versions of Crowd. One is the most stable version, also known as long term support or LTS version, which is recommended for most users. At the time of recording this video, that's version 18.16 0.1. And there's always a new version which is experimental and it might not be stable. I want you to install the LTS version, also taking into account that in the future, when you are watching this video, chances are that the LTS version might be Neva. If you're worried that this course is going to get outdated, don't worry because in this course, we are going to focus on the fundamentals. So I'm going to work with the core modules of the node. These core modules are stable. They have been there for a long time. So the code that we are going to write in this course will continue to work with the future versions of the node. Once you master the fundamentals, you can always learn about the new features that come in every version by looking at the change low. So let's not worry about the fancy new features in node and focus on the fundamentals. So let's go ahead and install the latest version node. You can see here, I get a packet, run the package. It's an installer. Ran the permission run, and the preparation will start installed and all. It will take some time. We next, agree to the terms and conditions and quick net. You may change the part. I will recommend to stick to this. Next, again, net. And you can check this spot whatever makes the dependencies. Istall again, it will take some time to install, no. Now the installation is complete. It's quite simple and easy, and it just take a few seconds. And now you have the terminal to install dependencies. Just follow the instructions and you're good to go. Now, back to the terminal, real write node, space, dash dash version one more time. And see, I've upgraded my node version to 18.16 p one. Next, we're going to write our first node program. 6. 6. Your First Steps in Node.js Programming: All right, now we are all set to write our first node program, so I'll quickly make a folder and go into that folder with C first underscore app. And now I'll open this in VS code using code period. VS code is my preferred code editor, but you may use any other code editor available in the market. I'll quickly make a file and the Js and I'll write a function using arrow function. As, I'll say hello. This will take an argument first name, and I'll just write sole log. Hello, and I'll pass the argument first name. That's my first node program, and I'll just call this program by writing say hello. I'll pass the parameter as my name hi. Now, back to the terminal. I'll execute this code using Node and write the name of the file app dot js. As you can see, it worked fine. Hello Shiva. Now let me show you something else. I'll amend this out and console log window, back to the terminal. I'll run node app dot js again. H. As you can see, we got an error. This window is not defined. So node, as you before is a C plus plus program. It includes Chrome's Vd JavaScript engine. But this app the JS file we passed node. Node gave it to Vd for execution. Now, back to or error, window is not defined. As it you before, in node, we don't have the Window or document objects. These are part of the runtime environment that we get with browsers. In node, we have other objects to work with files with the operating system, with the network, and so on. And that's what you're going to learn about in the next section. I hope you enjoyed this section, and thank you for watching.