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Getting Started with NodeJS
In this article, I am going to introduce NodeJS with Node Package Module (NPM), step-by-step basic implementation and explanation.
This article covers the following areas of NodeJS.
NodeJS uses an event-driven, non-blocking I/O model that makes it lightweight and efficient
Installation of NodeJS and NPM is straightforward using the installer package available at NodeJS official web site.
Now, test NodeJS by printing its version using the following command in Command Prompt:
1. > node -vand test npm by printing its version using command
1. > npm -vSimple way to test nodeJS work in your system is to create a javascript file which print a message.
Lets create app.js file
/* app.js file */
console.log("Node is working");Run the app.js file using Node command > node app.js in command prompt.
E:\> node -v
v14.16.0
E:\> npm -v
v6.14.11
E:\> node app.js
Node is working
E:\>You are done with installation.
1 > npm installThis command is finding a json file named as
package.json in root directory to install all dependencies defined in the file.{
"name": "ApplicationName",
"version": "0.0.1",
"description": "Application Description",
"main": "app.js",
"scripts": {
"start": "node app.js"
},
"repository": {
"type": "git",
"url": "https://github.com/npm/npm.git"
},
"dependencies": {
"express": "~3.0.1",
"sequelize": "latest",
"q": "latest",
"tedious": "latest",
"angular": "latest",
"angular-ui-router": "~0.2.11",
"path": "latest",
"dat-gui": "latest"
}
}The most important things in your package.json are name and version. Those are actually required, and your package won't install without them. The name and version together form an identifier that is assumed to be completely unique. Changes to the package should come along with changes to the version.
Repository
{
"repository": {
"type": "git",
"url": "https://github.com/npm/npm.git"
}
}Specify the place where your code lives. Through this repository, developers can reach out and contribute to your application. If the git repository is not GitHub, then the
npm docs command will be able to find you.{
"scripts": {
"start": "node app.js"
}
}Some default script values are based on package contents.
1 "start": "node app.js"If there is a app.js file in the root of your package, then npm will default the start command to node app.js.
{
"dependencies": {
"express": "~3.0.1",
"sequelize":"latest",
"q":"latest",
"tedious":"latest",
"angular":"latest",
"angular-ui-router": "~0.2.11",
"path":"latest",
"dat-gui":"latest"
}
}If you want to install the
latest version of a file, you just have to put latest in place of the version name.Tilde(~) is used to tell "Approximately equivalent to version".
Create a app.js javascript file with following code
/*app.js*/
const http = require('http');
const hostname = '127.0.0.1';
const port = 3000;
const server = http.createServer(function(req, res) {
res.statusCode = 200;
res.setHeader('Content-Type', 'text/plain');
res.end('Hello World\n');
});
server.listen(port, hostname, function() {
console.log('Server running at http://'+ hostname + ':' + port + '/');
})As we need
http to create an http server we use require('http') and pass it to a variable named http1 var http = require('http');We also need to defined hostname and port number, here we use
localHost i.e 127.0.0.1 and port number 3000 and assign this to the variables hostname and port, respectively.var hostname = '127.0.0.1';
var port = 3000;Next we create the http server using the
createServer method.var server = http.createServer(function(req, res){
res.statusCode = 200;
res.setHeader('Content-Type', 'text/plain');
res.end('Hello World\n');
});This created the server as well as a response having
statusCode: 200, Content-Type header of plain text and and ends with the string Hello World. This is the response that the server can send to browser.the function has two parameters
req and res which is the request from and response to the server, respectively.In our example we are creating responses.
We created the server, now we have to assign it a hostname and port number.
server.listen(port, hostname, function() {
console.log('Server running at http://'+ hostname + ':' + port + '/');
});Here, the server listens to localhost on port 3000 and prints "Server running at http://127.0.0.1:3000/" in command prompt.
Now Run app.js file un node using command
node appOpen a browser and enter url http://127.0.0.1:3000/. The browser will display Hello World message on the screen.
Now Run app.js file in node using command
E:\ >node app.js
Server running at http://127.0.0.1:3000/
If you've reached this point, thank you very much. I hope that this tutorial has been helpful for you and I'll see you all in the next.
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