Video tutorial recommendation:nodejs tutorial

##Node. js has become an integral part of IT. With its own package manager NPM, Node can discover many very useful libraries and frameworks.

In this article, I will show you some possibilities of building complex dynamic applications using Node.js.

1. Chalk: Set output style in terminal

During development of new Node.js application

console.logEssential, whether we use it to output errors, system data or output of functions and co. This does cause some confusion, however, because by default theconsole.logfunction outputs plain white text in the terminal.

Chalk changes that.

Just install Chalk as usual with

npm install chalkfrom https://www.npmjs.com/package/chalk.

This is a code example, below is what it actually looks like in my terminal.

const chalk = require(‘chalk’) // just blue font console.log(chalk.blue(‘this is lit’)) // blue & bold font, red background (bg = background) console.log(chalk.blue.bgRed.bold(‘Blue & Bold on Red’)) // blue font, red background console.log(chalk.blue.bgRed(‘Regular Blue on Red’)) // combining multiple font colors console.log(chalk.blue(‘Blue’) + ‘ Default’ + chalk.red(‘ Red’)) // Underlining text console.log(chalk.red(‘There is an ‘, chalk.underline(‘Error’))) // Using RGB-colors console.log(chalk.rgb(127, 255, 0).bold(‘Custom green’))

Output:

2. Morgan - Record all important information in the HTTP request

Again, this is particularly useful in the development of applications. Because HTTP requests are the heartbeat of the digital world, it's so important to have full control over everything in your application that affects them.

Morgan provides great information on this.

As usual, get it from https://www.npmjs.com/package/morgan via

npm install morganIn morgan we can define what we want to get about Requested information.

As stated in the documentation of the description, this is simply passed into the morgan middleware, so we will use it in the code example below.

const express = require(‘express’) const morgan = require(‘morgan’) const app = express() app.use( morgan( ‘:method :url :status :response-time ms’ )) app.get(‘/’, function(req, res) { res.send(‘hello, world!’) }) app.listen(8080)

So we want to get the following details about the incoming HTTP request: the method, the requested URL, the status of the request, and the time it took to respond.

When we open the website in the browser, running this code should result in the following output:

When we open the page in the browser, it always Making a GET-Request to the server, since we requested

/, Morgan will show this as well, and our "hello, world!" site was delivered successfully - which means status code 200. The entire execution takes about 2.3 milliseconds, which is pretty fast.

But not only do we ask for our website, but the browser always asks for a favicon, not found - error status 404.

Let's measure an experiment: We change the code so that there is a 200ms pause before each response. Here are the changes in the code:

app.get(‘/’, function(req, res) { setTimeout(function() { res.send(‘hello, world!’) }, 200) })

Now, when we request the page again in the browser, morgan will log this:

Now, The response took over 200 milliseconds - just like we wanted. But in the end, the page was successfully delivered again, except for the favicon, which we don't have now, and that only took a few MS, since we were only delaying requests to the

/route.

3. Cheerio: Use jQuery-like syntax to process the DOM that already exists on the server

Especially when we do not provide static HTML files but Cheerio is very useful when it comes to dynamic websites. We can modify the request's HTML code directly between the browser's request and response, without the client knowing. This is especially easy thanks to the jQuery-like syntax. Of course, you can also use Cheerio for crawling and many other operations.

Use

npm install cheerioInstall from https://www.npmjs.com/package/cheerio. With Cheerio we can get information about the structure and content of HTML:

const template = ` 
 
Welcome on our site
 
 ` const $ = cheerio.load(template) console.log($(‘h1’).text()) // Welcome on our site

Add HTML to an existing template:

let template = ` 
 
Welcome on our site
 
 ` const $ = cheerio.load(template) $(‘div’).append(‘
Paragraph
’) template = $.html()

Current template:

 
Welcome on our site
 
Paragraph
 

But Cheerio is the most A common situation might be to subsequently write content to a template:

let template = ` 
 
 
 ` const $ = cheerio.load(template) $(‘h1’).append(‘New welcome message!’) template = $.html()

Now the template:

 
New welcome message!
 

And, you can do a lot more with Cheerio. Just check out the documentation!

For more programming-related knowledge, please visit:

Introduction to Programming! !

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