Node then runs the JavaScript in that file and prints "Hello World". Running plain JavaScript is fun and all, but not very useful. This is why Node. In this first example I'm going to open a log file and parse it. What this log data means is not important, but basically each message contains a date, a letter, and a value. I want to add up the values for each letter. Fortunately Node. The fs module has a function named readFile that takes a file path and a callback.
The callback will be invoked when the file is done being read. The file data comes in the form of a Buffer , which is basically a byte array. We can convert it to a string using the toString function. Now let's add in the parsing. This is pretty much normal JavaScript so I will not go into any details. Now when you pass this file as the argument to the node command it will print the result and exit.
I use Node. It's much easier and a more powerful alternative to bash scripts. As you saw in the previous example, the typical pattern in Node. Basically you're telling it to do something and when it's done it will call your function callback. This is because Node is single-threaded.
While you're waiting on the callback to fire, Node can go off and do other things instead of blocking until the request is finished. This is especially important for web servers. It's pretty common in modern web applications to access databases.
While you're waiting for the database to return results Node can process more requests. This allows you to handle thousands of concurrent connections with very little overhead, compared to creating a separate thread for each connection. Like I said before Node doesn't do anything out of the box. One of the built-in modules makes it pretty easy to create a basic HTTP server , which is the example on the Node. When I say basic, I mean basic. This is not a full-featured HTTP server.
It can't serve any HTML file or images. In fact, no matter what you request, it will return 'Hello World'. You might notice something a little different now. Your Node. This is because you created a server and your Node. If you want this to be a full-featured web server, then you have to do that work. You have to check what was requested, read the appropriate files, and send the content back.
There's good news, though. People have already done this hard work for you. Express is a framework that makes creating most normal websites very simple. The first thing you have to do it install it. Along with the node command you also have access to a command called "npm". This tool gives you access to an enormous collection of modules created by the community, and one of them is Express.
You can now require it like any built-in module. Let's create a basic static file server using Express. You now have a pretty capable static file server. The Express development environment includes an installation of Nodejs , the NPM package manager , and optionally the Express Application Generator on your local computer. Node and the NPM package manager are installed together from prepared binary packages, installers, operating system package managers or from source as shown in the following sections.
Express is then installed by NPM as a dependency of your individual Express web applications along with other libraries like template engines, database drivers, authentication middleware, middleware to serve static files, etc.
The application generator is optional because you don't need to use this tool to create apps that use Express, or construct Express apps that have the same architectural layout or dependencies. We'll be using it though, because it makes getting started a lot easier, and promotes a modular application structure. Note: Unlike some other web frameworks, the development environment does not include a separate development web server. There are other peripheral tools that are part of a typical development environment, including text editors or IDEs for editing code, and source control management tools like Git for safely managing different versions of your code.
We are assuming that you've already got these sorts of tools installed in particular a text editor. There is a full list on the nodejs Downloads page. Almost any personal computer should have the necessary performance to run Node during development. Express is run in a Node environment, and hence can run on any platform that runs Node.
Generally you should use the most recent LTS long-term supported release as this will be more stable than the "current" release while still having relatively recent features and is still being actively maintained.
You should use the Current release if you need a feature that is not present in the LTS version. Other dependencies, such as database drivers, template engines, authentication engines, etc. We'll discuss them in later app-specific articles. If you're using another OS or just want to see some of the other approaches for the current platforms then see Installing Node. The easiest way to install the most recent LTS version of Node This can be done by running the following two commands on your terminal:.
Warning: Don't install directly from the normal Ubuntu repositories because they contain very old versions of node. The Nodejs package manager NPM should also have been installed, and can be tested in the same way:. As a slightly more exciting test let's create a very basic "pure node" server that prints out "Hello World" in the browser when you visit the correct URL in your browser:. Note: Don't worry if you don't understand exactly what this code is doing yet! We'll explain our code in greater detail once we start using Express!
Note: From Node's perspective, Express is just another package that you need to install using NPM and then require in your own code. VS Code has an integrated terminal which you can use to run shell commands.
You can run Node. For this walkthrough, you can use either an external terminal or the VS Code integrated terminal for running the command-line tools. As mentioned in the introduction, VS Code ships with a debugger for Node.
Let's try debugging our simple Hello World application. To set a breakpoint in app. A red circle will appear in the gutter. You can now click Debug toolbar green arrow or press F5 to launch and debug "Hello World".
Your breakpoint will be hit and you can view and step through the simple application. Note: We're done with the "Hello World" example so navigate out of that folder before you create an Express app.
You can delete the "Hello" folder if you want as it is not required for the rest of the walkthrough. Express is a very popular application framework for building and running Node. You can scaffold create a new Express application using the Express Generator tool. The Express Generator is shipped as an npm module and installed by using the npm command-line tool npm.
Tip: To test that you've got npm correctly installed on your computer, type npm --help from a terminal and you should see the usage documentation. The -g switch installs the Express Generator globally on your machine so you can run it from anywhere. This creates a new folder called myExpressApp with the contents of your application.
The --view pug parameters tell the generator to use the pug template engine. To install all of the application's dependencies again shipped as npm modules , go to the new folder and execute npm install :. At this point, we should test that our application runs. The generated Express application has a package.
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