Running javascript in node js

Node.js tutorial in Visual Studio Code

Node.js is a platform for building fast and scalable server applications using JavaScript. Node.js is the runtime and npm is the Package Manager for Node.js modules.

Visual Studio Code has support for the JavaScript and TypeScript languages out-of-the-box as well as Node.js debugging. However, to run a Node.js application, you will need to install the Node.js runtime on your machine.

To get started in this walkthrough, install Node.js for your platform. The Node Package Manager is included in the Node.js distribution. You’ll need to open a new terminal (command prompt) for the node and npm command-line tools to be on your PATH.

To test that you have Node.js installed correctly on your computer, open a new terminal and type node —version and you should see the current Node.js version installed.

Linux: There are specific Node.js packages available for the various flavors of Linux. See Installing Node.js via package manager to find the Node.js package and installation instructions tailored to your version of Linux.

Windows Subsystem for Linux: If you are on Windows, WSL is a great way to do Node.js development. You can run Linux distributions on Windows and install Node.js into the Linux environment. When coupled with the WSL extension, you get full VS Code editing and debugging support while running in the context of WSL. To learn more, go to Developing in WSL or try the Working in WSL tutorial.

Hello World

Let’s get started by creating the simplest Node.js application, «Hello World».

Create an empty folder called «hello», navigate into and open VS Code:

mkdir hello cd hello code . 

Tip: You can open files or folders directly from the command line. The period ‘.’ refers to the current folder, therefore VS Code will start and open the Hello folder.

From the File Explorer toolbar, press the New File button:

By using the .js file extension, VS Code interprets this file as JavaScript and will evaluate the contents with the JavaScript language service. Refer to the VS Code JavaScript language topic to learn more about JavaScript support.

Create a simple string variable in app.js and send the contents of the string to the console:

var msg = 'Hello World'; console.log(msg); 

Note that when you typed console. IntelliSense on the console object was automatically presented to you.

Also notice that VS Code knows that msg is a string based on the initialization to ‘Hello World’ . If you type msg. you’ll see IntelliSense showing all of the string functions available on msg .

After experimenting with IntelliSense, revert any extra changes from the source code example above and save the file ( ⌘S (Windows, Linux Ctrl+S ) ).

Running Hello World

It’s simple to run app.js with Node.js. From a terminal, just type:

You should see «Hello World» output to the terminal and then Node.js returns.

Integrated Terminal

VS Code has an integrated terminal which you can use to run shell commands. You can run Node.js directly from there and avoid switching out of VS Code while running command-line tools.

View > Terminal ( ⌃` (Windows, Linux Ctrl+` ) with the backtick character) will open the integrated terminal and you can run node app.js there:

For this walkthrough, you can use either an external terminal or the VS Code integrated terminal for running the command-line tools.

Debugging Hello World

As mentioned in the introduction, VS Code ships with a debugger for Node.js applications. Let’s try debugging our simple Hello World application.

To set a breakpoint in app.js , put the editor cursor on the first line and press F9 or click in the editor left gutter next to the line numbers. A red circle will appear in the gutter.

To start debugging, select the Run and Debug view in the Activity Bar:

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. Notice that VS Code displays a different colored Status Bar to indicate it is in Debug mode and the DEBUG CONSOLE is displayed.

Now that you’ve seen VS Code in action with «Hello World», the next section shows using VS Code with a full-stack Node.js web app.

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.

An Express application

Express is a very popular application framework for building and running Node.js applications. 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.

Install the Express Generator by running the following from a terminal:

npm install -g express-generator 

The -g switch installs the Express Generator globally on your machine so you can run it from anywhere.

We can now scaffold a new Express application called myExpressApp by running:

express myExpressApp --view pug 

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 :

cd myExpressApp npm install 

At this point, we should test that our application runs. The generated Express application has a package.json file which includes a start script to run node ./bin/www . This will start the Node.js application running.

From a terminal in the Express application folder, run:

The Node.js web server will start and you can browse to http://localhost:3000 to see the running application.

Great code editing

Close the browser and from a terminal in the myExpressApp folder, stop the Node.js server by pressing CTRL+C .

Note: If you’ve been using the VS Code integrated terminal to install the Express generator and scaffold the app, you can open the myExpressApp folder from your running VS Code instance with the File > Open Folder command.

The Node.js and Express documentation does a great job explaining how to build rich applications using the platform and framework. Visual Studio Code will make you more productive in developing these types of applications by providing great code editing and navigation experiences.

Open the file app.js and hover over the Node.js global object __dirname . Notice how VS Code understands that __dirname is a string. Even more interesting, you can get full IntelliSense against the Node.js framework. For example, you can require http and get full IntelliSense against the http class as you type in Visual Studio Code.

VS Code uses TypeScript type declaration (typings) files (for example node.d.ts ) to provide metadata to VS Code about the JavaScript based frameworks you are consuming in your application. Type declaration files are written in TypeScript so they can express the data types of parameters and functions, allowing VS Code to provide a rich IntelliSense experience. Thanks to a feature called Automatic Type Acquisition , you do not have to worry about downloading these type declaration files, VS Code will install them automatically for you.

You can also write code that references modules in other files. For example, in app.js we require the ./routes/index module, which exports an Express.Router class. If you bring up IntelliSense on index , you can see the shape of the Router class.

Debug your Express app

You will need to create a debugger configuration file launch.json for your Express application. Click on Run and Debug in the Activity Bar ( ⇧⌘D (Windows, Linux Ctrl+Shift+D ) ) and then select the create a launch.json file link to create a default launch.json file. Select the Node.js environment by ensuring that the type property in configurations is set to «node» . When the file is first created, VS Code will look in package.json for a start script and will use that value as the program (which in this case is «$\\bin\\www ) for the Launch Program configuration.

 "version": "0.2.0", "configurations": [   "type": "node", "request": "launch", "name": "Launch Program", "program": "$ \\bin\\www"  >  ] > 

Save the new file and make sure Launch Program is selected in the configuration dropdown at the top of the Run and Debug view. Open app.js and set a breakpoint near the top of the file where the Express app object is created by clicking in the gutter to the left of the line number. Press F5 to start debugging the application. VS Code will start the server in a new terminal and hit the breakpoint we set. From there you can inspect variables, create watches, and step through your code.

Deploy your application

If you’d like to learn how to deploy your web application, check out the Deploying Applications to Azure tutorials where we show how to run your website in Azure.

Next steps

There is much more to explore with Visual Studio Code, please try the following topics:

• Node.js profile template — Create a new profile with a curated set of extensions, settings, and snippets.
• Settings — Learn how to customize VS Code for how you like to work.
• Debugging — This is where VS Code really shines.
• Video: Getting started with Node.js debugging — Learn how to attach to a running Node.js process.
• Node.js debugging — Learn more about VS Code’s built-in Node.js debugging.
• Debugging recipes — Examples for scenarios like client-side and container debugging.
• Tasks — Running tasks with Gulp, Grunt and Jake. Showing Errors and Warnings.

Источник

How to run js file in Node.js

To run a JavaScript file using Node.js, you need to use the node command followed by the file name. For example, if you have a file named script.js , you can run it using the following command:

You can also pass arguments to your script by appending them to the node command after the file name. For example, if your script takes in two arguments, you can run it like this:

Keep in mind that you need to have Node.js installed on your computer to run JavaScript files using the node command. You can check if you have Node.js installed by running the following command:

If you don’t have Node.js installed, you can download and install it from the official Node.js website.

¶Node: Run js file in experimental mode

To run a JavaScript file using Node.js in experimental mode, you need to use the —experimental-modules flag when running the node command. This flag enables support for the ECMAScript Modules (ESM) proposal, which allows you to use the import and export statements in your code.

For example, if you have a file named script.mjs that uses the import statement, you can run it using the following command:

node --experimental-modules script.mjs 

Remember that the —experimental-modules flag is only available in Node.js version 13.2.0 or higher. You can check your Node.js version by running the node -v command.

Additionally, you must ensure that your JavaScript file has the .mjs file extension for Node.js to treat it as an ECMAScript module. This is because the import and export statements are only allowed in files with the .mjs extension when the —experimental-modules flag is used.

For more information on ECMAScript modules and how to use them in Node.js, you can refer to the official Node.js documentation.

¶What is Node.js

Node.js is an open-source, cross-platform runtime environment that allows developers to create server-side and networking applications using JavaScript. It is built on top of the Google Chrome V8 JavaScript engine, allowing developers to create scalable and high-performance applications using a non-blocking, event-driven I/O model.

Ryan Dahl created Node.js in 2009, and it has since become one of the most popular server-side JavaScript environments. Many companies and organizations use it, including Microsoft, Netflix, PayPal, Uber, and eBay.

One of the main advantages of using Node.js is that it allows developers to use JavaScript on the server side, which makes it possible to share code between the server and the client. This allows for more efficient and organized development, as well as easier maintenance of applications.

Node.js also has a large and active community, contributing many modules and packages that can be easily installed and used in Node.js applications. This makes it easy for developers to extend their applications’ functionality and leverage others’ work in the community.

Overall, Node.js is a powerful and popular runtime environment for developing server-side and networking applications. It allows developers to use JavaScript on the server side and take advantage of its many modules and packages to build efficient and scalable applications.

Related video

Источник