In this article we'll see how to set up a Node.js project with a package.json file so that you can easily install other dependencies using NPM. This also shows how you'll use NodeJS' module pattern to create projects which is a collection of many files and packages.
Prerequisite to creating a project is that Node.js is installed in your system (which also install NPM) and you have an IDE like Visual Studio Code.
Check this post How to Install Node.js and NPM in Windows to see how to install Node.js
Setting up NodeJS project
To start with, let's create a new directory and you can name it nodeapp or any other meaningful name. If you open this directory in Visual Studio Code as expected you won't have anything with in it!
In order to make it a Node project you'll have to use the command npm init which creates a package.json file by asking
you few questions. If you want to bypass these questions and answer "yes" by default for all the questions you can use
npm init -y command instead.
Go to the directory you have just created and run the npm init command to initialize your Node project.
nodeapp>npm init
This utility will walk you through creating a package.json file.
It only covers the most common items, and tries to guess sensible defaults.
See `npm help init` for definitive documentation on these fields
and exactly what they do.
Use `npm install <pkg>` afterwards to install a package and
save it as a dependency in the package.json file.
Press ^C at any time to quit.
package name: (nodeapp)
version: (1.0.0)
description: A node project
entry point: (index.js)
test command:
git repository:
keywords:
author:
license: (ISC)
About to write to D:\NETJS\NetJS_2017\NodeJS\nodeapp\package.json:
{
"name": "nodeapp",
"version": "1.0.0",
"description": "A node project",
"main": "index.js",
"scripts": {
"test": "echo \"Error: no test specified\" && exit 1"
},
"author": "",
"license": "ISC"
}
Is this OK? (yes)
As you can see for most of the questions asked, I have just pressed enter, only entry is for the "description". You can always go later to the created package.json file and edit it so no worries.
If you go to Visual Studio code now you should see the generated package.json file.
Since the starting file is named as "index.js" so let's create such a file in our "nodeapp" project.
index.js
console.log("It's a new Node project");
Running this JavaScript file should output the content as expected.
node index.js It's a new Node project
Now let's change our package.json a little and add a kay-value entry in the "scripts" section.
"scripts": {
"test": "echo \"Error: no test specified\" && exit 1",
"start": "node index.js"
},
This instructs Node to use start script as the executor of the command given as value "node index.js". Now you can use
npm start command to start your project.
npm start > nodeapp@1.0.0 start > node index.js It's a new Node project
Importing packages in NodeJS
Let's try to import and use modules in our code files. To start with we'll import built-in Node modules for which you don't need any extra installation as these modules are already there in NodeJS.
We'll use fs and path modules to write a file. The 'fs' module is used to handle the file system and the 'path' module is used to handle file paths.
In order to use these modules, you'll need to import them, in NodeJS you can do it as given below.
const fs = require('fs');
const path = require('path');
Using writeFile() method of the fs package we'll write to a file in Node.js. Here is the description of the writeFile() method.
fs.writeFile( file, data, options, callback )
- file: Path of the file where it has to be written.
- data: The data you want to write to the file.
- options: To specify optional parameters like encoding
- callback: It is the function that would be called when the method is executed.
index.js
Here is the modified index.js file.
const fs = require('fs');
const path = require('path');
console.log(__dirname);
console.log("It's a new Node project");
const content = "A test file";
fs.writeFile(path.join(__dirname, 'test.txt'), content, (err) => {
if (err)
console.log(err);
else {
console.log("File written successfully\n");
}
});
Note that __dirname is a variable that tells you the absolute path of the directory containing the currently executing file. Using path.join() method an absolute path for the file is given.
If you run npm start command now you should see a file "test.txt" created within your root project directory.
Installing third party packages in Node project
In the above example we used built-in modules that don’t need any installation but you will definitely use many other
third-party packages that would need installation. For that you will use
In our project we'll try to install Nodemon package that helps develop Node.js based applications by automatically restarting the node application when file changes in the directory are detected.
To see Nodemon in use we'll change the index.js to create a HTTP Server using Node.jsindex.js
const http = require('http');
const hostname = 'localhost';
const port = 3000;
const requestListener = function(req, res){
res.statusCode = 200;
res.setHeader('Content-Type', 'text/plain');
res.write('Hello World');
res.write(' From NodeJS\n');
res.end();
}
const server = http.createServer(requestListener);
server.listen(port, hostname, () => {
console.log(`Server running at http://${hostname}:${port}/`);
});
If you run the npm start command now and go to the URL http://localhost:3000/ once the server is started you should see the response as sent by the server.
If we make a slight change in the code now and change the line from res.write(' From NodeJS\n'); to this
res.write(' From NodeJS Project\n');
Above change won't be reflected automatically and you'll have to stop the server and restart it to get this change reflected. That's where Nodemon can help as it automatically restarts the node application when file changes are detected.
npm install options
You can control where and how the specified packages get saved by using some additional flags with npm install
-P, --save-prod: Package will appear in your dependencies. You'll use this option if you want the installed package to be part of production build too. This is the default also
-D, --save-dev: Package will appear in your devDependencies. You'll use this option if you want the installed package to be used during development only.
-O, --save-optional: Package will appear in your optionalDependencies.
--no-save: Prevents saving to dependencies.
It makes sense to install Nodemon as dev dependency so use the following command to install Nodemon.
npm install nodemon --save-dev
Once the installation is done if you go back to your project structure you'll see some new directories and files like
package-lock.json and node_modules folder.
package-lock.json- Provides version information for all packages installed into node_modules by the npmclient.
node_modules- Provides npm packages to the entire workspace. That's the directory where packages are installed.
In the package.json file now you'll see a "devDependencies" entry.
"devDependencies": {
"nodemon": "^3.1.0"
}
You'll need to make one more change in the start script to start using nodemon rather than node.
"start": "nodemon index.js"
With that if you use npm start command.
npm start > nodeapp@1.0.0 start > nodemon index.js [nodemon] 3.1.0 [nodemon] to restart at any time, enter `rs` [nodemon] watching path(s): *.* [nodemon] watching extensions: js,mjs,cjs,json [nodemon] starting `node index.js` Server running at http://localhost:3000/
If you make changes in index.js file you can see that the application starts automatically now.
[nodemon] restarting due to changes... [nodemon] starting `node index.js` Server running at http://localhost:3000/
That's all for this topic How to Setup a Node.js Project. If you have any doubt or any suggestions to make please drop a comment. Thanks!
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