Noah Saunders

Noah Saunders

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How to Build CRUD Application using Node.js and MongoDB?

Node.js is the most popular JavaScript framework when it comes to high-speed application development. Node.js Professionals often opt for a NoSQL database which can keep up with Node.js speed all while maintaining the performance of the application. MongoDB is a perfect fit for this kind of requirement as it has a very fast development cycle and performs quite efficiently. Thus, I bring you this Node.js MongoDB tutorial where I will be demonstrating how effortlessly you can develop an application using Node.js with MongoDB from scratch.

How to Build CRUD Application using Node.js and MongoDB

Below are the topics I will be covering in this Node.js MongoDB tutorial:

  • What is NoSQL Database?
  • Introduction to MongoDB
  • Node.js MongoDB Demo

So, let’s get started.

What is NoSQL Database?

Not only SQL database or more popularly known as NoSQL database is a database design approach that provides a mechanism to store and access a wide variety of unstructured data. This unstructured data can contain a mixture of data models, including key-value, document, columnar and graph formats, etc. NoSQL database is especially useful for handling humongous sets of distributed data. These databases have a dynamic schema and no specific query language along with no or very fewer relationships. But it stores the data in the form of collections and documents which enable quick updates.

There is a list of NoSQL databases which are used quite heavily in the industry, some of which I have listed below:

  1. MongoDB
  2. Hbase
  3. Cassandra
  4. Amazon SimpleDB
  5. Hypertable

In this article, I will be focusing on only one of these databases, which by now you might have guessed, that is MongoDB. But before I show you how to work with it, let’s get familiar with its nitty-gritty.

Introduction to MongoDB

MongoDB is an open source non-relational database that stores the data in the form of collections and documents. This kind of databases preserves most of the functionalities while offering horizontal scalability. This eases the work of a developer by providing persistence to the data and enhancing agility.

MongoDB stores the JSON documents in the form of collections having dynamic schemas. It stores all the related information together which enhances the speed of query processing. This way, it also helps in bringing down the gap between the key-value stores and relational databases.

Below I have listed down a few of the most intriguing features of MongoDB:

  • Indexing: It makes use of indexes that helps in improving the search performance.
  • Replication: MongoDB distributes the data across different machines.
  • Ad-hoc Queries: It supports ad-hoc queries by indexing the BSON documents & using a unique query language.
  • Schemaless: It enhances the flexibility of the data and needs no script to modify or update data.
  • Sharding: It makes use of sharding which eases the deployment of very large data sets and provides high throughput operations.

Now that you are familiar with MongoDB, let’s move ahead with this article and see how simple it is to install MongoDB in the system.

MongoDB Installation

Step I: Download the latest version MongoDB server from its official site: https://www.mongodb.com/download-center/community

Step II: Next click on the ‘Server’ tab as shown in the below screenshot.

How to Build CRUD Application using Node.js and MongoDB

Step III: If you are looking for any specific version, you can select it from the drop-down list or you can just download the latest version.

Step IV: Select your OS from the drop down. Since I am working on Windows I will go for Windows 64 bit.

Step V: Now, select the package as MSI.

Step VI: Finally, click on ‘Download’ to begin the download process.

Step VII: Once downloaded, double click on the MSI file to open it and proceed with the installation wizard.
How to Build CRUD Application using Node.js and MongoDB

Step VIII: Now, in order to start the MongoDB server you have to run the .exe file and assign the database folder. To make the work easier, all you need to do is write down a few lines of code in a notepad file and save it with the .bat extension. In other words, you just need to create a batch file, which will start the MongoDB server for you without any hassle. To create the batch file type in the below code:

cd C:Program FilesMongoDBServer.0in (MongoDB path)
mongod.exe --dbpath F:MongoDBdata (database dump destination)

Now, whenever you want to launch the MongoDB server, all you need to do is double click this batch file and open the MongoDB Compass application.

Step IX: Next, you need to launch the ‘MongoDB Compass’ and agree to its terms of use.
How to Build CRUD Application using Node.js and MongoDB

Step X: Now you need to provide the server configurations and hit ‘Connect’.
How to Build CRUD Application using Node.js and MongoDB

Step XI: Next, click on ‘Create Database’.
How to Build CRUD Application using Node.js and MongoDB

Step XII: Now, provide a relevant name for your database and collection and hit ‘Create Database’.
How to Build CRUD Application using Node.js and MongoDB

I guess, now you are all set to get started with the practical part, so without any more delay let’s dive into the code.

Node.js MongoDB Demo

Here I will be creating a CRUD application for Course Management with the help of Node.js and Express.js and use MongoDB to store the data. In this application, I will be taking course details like name, id, duration, and fee as inputs. For that, I will be creating a few view files which will act as an interface. Then in order to handle the data, I will be needing a controller as well which will help in manipulating the data. Finally, I will be needing a few model files to store the data. So basically, I will be following an MVC pattern for this application development. So, lets now jump into development.

Our application will be having the following hierarchy:

NodejsMongoDbDemo

  • package.json
  • script.js
  • controllers
  1. courseController.js
  • img
  1. logo.jpg
  • models
  1. course.model.js
  2. mongodb.js
  • views
  1. course

a. courseAddEdit.hbs

b. list.hbs

2. layouts

  • mainLayout.hbs

So, let’s begin the application development by creating a directory for the project. Once you are done, open the command prompt and navigate to your project directory. Now you need to set up the project configurations for that, type in the below command and provide the necessary details:

npm init

Now, you need to install the required packages. So, in this project, I am using the below packages:

  • express.js: It is a web framework.
  • express-handlebars: It is a template engine and helps in creating client-side applications.
  • mongoose: Helps in communicating with MongoDB.
  • body-parser: Helps in converting the POST data into the request body.
  • nodemon: Helps in automatically restarting the server whenever the code changes.

In order to install these packages, type in the following command:

npm i --s express express-handlebars mongoose body-parser

Since I want to install nodemon such that it can access any file in the directory, I will be installing it with the global command:

npm i -g nodemon

Once you are done installing with the packages, your final JSON file should look like the below file:

package.json

{
"name": "samplenodemongo",
"version": "1.0.0",
"description": "Edureka demo on how to build a Node.js application with MongoDB",
"main": "script.js",
"scripts": {
"test": "echo "Error: no test specified" && exit 1"
},
"author": "Edureka",
"license": "ISC",
"dependencies": {
"body-parser": "^1.19.0",
"express": "^4.16.4",
"express-handlebars": "^3.0.2",
"mongoose": "^5.5.6",
"nodemon": "^1.19.0"
}
}

As you can see, in the dependencies section all the installed packages have been successfully listed. So, lets now create the database we will be using in this demo. For that start the batch file and open MongoDB application. Now, create a new database and provide a collection name. In my application, I will be using ‘EdurekaCoursesDB’ as the database name and ‘courses’ as the collection.
How to Build CRUD Application using Node.js and MongoDB

Now, switch back to your code editor where we will be creating the files to establish connectivity between Node.js and MongoDB. For that, first, you need to create a folder inside the project directory and name it ‘model’. Inside this folder, create a javascript file with the name ‘ mongodb.js ‘ and type in the below code:

mongodb.js

const mongoose = require('mongoose');
 
mongoose.connect('mongodb://localhost:27017/EdurekaCoursesDB', {useNewUrlParser: true}, (err) => {
if (!err) {
console.log('Successfully Established Connection with MongoDB')
}
else {
console.log('Failed to Establish Connection with MongoDB with Error: '+ err)
}
});
 
//Connecting Node and MongoDB
require('./course.model');

Now, you need to define the schema of your course database. For that, create a new JS file within the model folder and name it ‘ course.model.js ‘. So, I am using four fields in my course object I am using four fields which are name, id, duration, and fee. To create this file, type in the below-given code.

course.model.js

const mongoose = require('mongoose');
 
//Attributes of the Course object
var courseSchema = new mongoose.Schema({
courseName: {
type: String,
required: 'This field is required!'
},
courseId: {
type: String
},
courseDuration: {
type: String
},
courseFee: {
type: String
}
});
 
mongoose.model('Course', courseSchema);

Now, you need to create the root file called ‘ script.js ‘. This file is the entry point of this application and will contain all the connection paths in it. You need to be really careful while providing the paths in this file as it might result in an error or application failure. Along with this, it is also responsible for invoking the server and establish the connection. In order to create this file, type in the below code:

script.js

require('./models/mongodb');
 
//Import the necessary packages
const express = require('express');
var app = express();
const path = require('path');
const exphb = require('express-handlebars');
const bodyparser = require('body-parser');
 
const courseController = require('./controllers/courseController');
 
app.use(bodyparser.urlencoded({
extended: true
}));
 
//Create a welcome message and direct them to the main page
app.get('/', (req, res) => {
res.send('
 
<h2 style="font-family: Malgun Gothic; color: midnightblue ">Welcome to Edureka Node.js MongoDB Tutorial!!</h2>
 
 
 Click Here to go to <b> <a href="/course">Course Page</a> </b>');
});
app.use(bodyparser.json());
 
//Configuring Express middleware for the handlebars
app.set('views', path.join(__dirname, '/views/'));
app.engine('hbs', exphb({ extname: 'hbs', defaultLayout: 'mainLayout', layoutDir: __dirname + 'views/layouts/' }));
app.set('view engine', 'hbs');
 
//Establish the server connection
//PORT ENVIRONMENT VARIABLE
const port = process.env.PORT || 8080;
app.listen(port, () => console.log(`Listening on port ${port}..`));
 
//Set the Controller path which will be responding the user actions
app.use('/course', courseController);

Next, in order to handle the user requests, you need to create the router file. For that first, create a folder and name it ‘controller’ and within this folder create a file with the name ‘ courseController.js ‘. In this file, we will be dealing with the CRUD operations related to the employee. Below is the code for creating this file:

courseController.js

//Import the dependencies
const express = require('express');
const mongoose = require('mongoose');
//Creating a Router
var router = express.Router();
//Link
const Course = mongoose.model('Course');
 
//Router Controller for READ request
router.get('/',(req, res) => {
res.render("course/courseAddEdit", {
viewTitle: "Insert a New Course for Edureka"
});
});
 
//Router Controller for UPDATE request
router.post('/', (req,res) => {
if (req.body._id == '')
insertIntoMongoDB(req, res);
else
updateIntoMongoDB(req, res);
});
 
//Creating function to insert data into MongoDB
function insertIntoMongoDB(req,res) {
var course = new Course();
course.courseName = req.body.courseName;
course.courseId = req.body.courseId;
course.courseDuration = req.body.courseDuration;
course.courseFee = req.body.courseFee;
course.save((err, doc) => {
if (!err)
res.redirect('course/list');
else
console.log('Error during record insertion : ' + err);
});
}
 
//Creating a function to update data in MongoDB
function updateIntoMongoDB(req, res) {
Course.findOneAndUpdate({ _id: req.body._id }, req.body, { new: true }, (err, doc) => {
if (!err) { res.redirect('course/list'); }
else {
if (err.name == 'ValidationError') {
handleValidationError(err, req.body);
res.render("course/courseAddEdit", {
//Retaining value to be displayed in the child view
viewTitle: 'Update Course Details',
employee: req.body
});
}
else
console.log('Error during updating the record: ' + err);
}
});
}
 
//Router to retrieve the complete list of available courses
router.get('/list', (req,res) => {
Course.find((err, docs) => {
if(!err){
res.render("course/list", {
list: docs
});
}
else {
console.log('Failed to retrieve the Course List: '+ err);
}
});
});
 
//Creating a function to implement input validations
function handleValidationError(err, body) {
for (field in err.errors) {
switch (err.errors[field].path) {
case 'courseName':
body['courseNameError'] = err.errors[field].message;
break;
default:
break;
}
}
}
 
//Router to update a course using it's ID
router.get('/:id', (req, res) => {
Course.findById(req.params.id, (err, doc) => {
if (!err) {
res.render("course/courseAddEdit", {
viewTitle: "Update Course Details",
course: doc
});
}
});
});
 
//Router Controller for DELETE request
router.get('/delete/:id', (req, res) => {
Course.findByIdAndRemove(req.params.id, (err, doc) => {
if (!err) {
res.redirect('/course/list');
}
else { console.log('Failed to Delete Course Details: ' + err); }
});
});
 
module.exports = router;//Import the dependencies
const express = require('express');
const mongoose = require('mongoose');
//Creating a Router
var router = express.Router();
//Link
const Course = mongoose.model('Course');
 
//Router Controller for READ request
router.get('/',(req, res) => {
res.render("course/courseAddEdit", {
viewTitle: "Insert a New Course for Edureka"
});
});
 
//Router Controller for UPDATE request
router.post('/', (req,res) => {
if (req.body._id == '')
insertIntoMongoDB(req, res);
else
updateIntoMongoDB(req, res);
});
 
//Creating function to insert data into MongoDB
function insertIntoMongoDB(req,res) {
var course = new Course();
course.courseName = req.body.courseName;
course.courseId = req.body.courseId;
course.courseDuration = req.body.courseDuration;
course.courseFee = req.body.courseFee;
course.save((err, doc) => {
if (!err)
res.redirect('course/list');
else
console.log('Error during record insertion : ' + err);
});
}
 
//Creating a function to update data in MongoDB
function updateIntoMongoDB(req, res) {
Course.findOneAndUpdate({ _id: req.body._id }, req.body, { new: true }, (err, doc) => {
if (!err) { res.redirect('course/list'); }
else {
if (err.name == 'ValidationError') {
handleValidationError(err, req.body);
res.render("course/courseAddEdit", {
//Retaining value to be displayed in the child view
viewTitle: 'Update Course Details',
employee: req.body
});
}
else
console.log('Error during updating the record: ' + err);
}
});
}
 
//Router to retrieve the complete list of available courses
router.get('/list', (req,res) => {
Course.find((err, docs) => {
if(!err){
res.render("course/list", {
list: docs
});
}
else {
console.log('Failed to retrieve the Course List: '+ err);
}
});
});
 
//Creating a function to implement input validations
function handleValidationError(err, body) {
for (field in err.errors) {
switch (err.errors[field].path) {
case 'courseName':
body['courseNameError'] = err.errors[field].message;
break;
default:
break;
}
}
}
 
//Router to update a course using it's ID
router.get('/:id', (req, res) => {
Course.findById(req.params.id, (err, doc) => {
if (!err) {
res.render("course/courseAddEdit", {
viewTitle: "Update Course Details",
course: doc
});
}
});
});
 
//Router Controller for DELETE request
router.get('/delete/:id', (req, res) => {
Course.findByIdAndRemove(req.params.id, (err, doc) => {
if (!err) {
res.redirect('/course/list');
}
else { console.log('Failed to Delete Course Details: ' + err); }
});
});
 
module.exports = router;//Import the dependencies
const express = require('express');
const mongoose = require('mongoose');
//Creating a Router
var router = express.Router();
//Link
const Course = mongoose.model('Course');
 
//Router Controller for READ request
router.get('/',(req, res) => {
res.render("course/courseAddEdit", {
viewTitle: "Insert a New Course for Edureka"
});
});
 
//Router Controller for UPDATE request
router.post('/', (req,res) => {
if (req.body._id == '')
insertIntoMongoDB(req, res);
else
updateIntoMongoDB(req, res);
});
 
//Creating function to insert data into MongoDB
function insertIntoMongoDB(req,res) {
var course = new Course();
course.courseName = req.body.courseName;
course.courseId = req.body.courseId;
course.courseDuration = req.body.courseDuration;
course.courseFee = req.body.courseFee;
course.save((err, doc) => {
if (!err)
res.redirect('course/list');
else
console.log('Error during record insertion : ' + err);
});
}
 
//Creating a function to update data in MongoDB
function updateIntoMongoDB(req, res) {
Course.findOneAndUpdate({ _id: req.body._id }, req.body, { new: true }, (err, doc) => {
if (!err) { res.redirect('course/list'); }
else {
if (err.name == 'ValidationError') {
handleValidationError(err, req.body);
res.render("course/courseAddEdit", {
//Retaining value to be displayed in the child view
viewTitle: 'Update Course Details',
employee: req.body
});
}
else
console.log('Error during updating the record: ' + err);
}
});
}
 
//Router to retrieve the complete list of available courses
router.get('/list', (req,res) => {
Course.find((err, docs) => {
if(!err){
res.render("course/list", {
list: docs
});
}
else {
console.log('Failed to retrieve the Course List: '+ err);
}
});
});
 
//Creating a function to implement input validations
function handleValidationError(err, body) {
for (field in err.errors) {
switch (err.errors[field].path) {
case 'courseName':
body['courseNameError'] = err.errors[field].message;
break;
default:
break;
}
}
}
 
//Router to update a course using it's ID
router.get('/:id', (req, res) => {
Course.findById(req.params.id, (err, doc) => {
if (!err) {
res.render("course/courseAddEdit", {
viewTitle: "Update Course Details",
course: doc
});
}
});
});
 
//Router Controller for DELETE request
router.get('/delete/:id', (req, res) => {
Course.findByIdAndRemove(req.params.id, (err, doc) => {
if (!err) {
res.redirect('/course/list');
}
else { console.log('Failed to Delete Course Details: ' + err); }
});
});
 
module.exports = router;

Now, that we are done with backend files, the next step is to create the Views. For that first, you need to create a wrapper for the child views. But before that, create a folder with name ‘ views’. Inside this folder create two more folders with names ‘ course’ and ‘ layouts’ respectively with .hbs extension. Now, navigate inside the ‘layouts’ folder and create the wrapper with the name ‘ mainLayout.hbs’. This file will contain the basic skeleton of the application which will be reflected in the child views as well. In this file, I am inserting an image as well, so for that I will create a local folder with name img and save my image inside.

To create this file, type in the below codes:

mainLayout.hbs

<!DOCTYPE html>
<html>
<head>
<title>Edureka Node.js MongoDB Demo</title>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
<img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" data-wp-preserve="%3Cscript%20src%3D%22https%3A%2F%2Fajax.googleapis.com%2Fajax%2Flibs%2Fjquery%2F3.2.1%2Fjquery.min.js%22%3E%3C%2Fscript%3E" data-mce-resize="false" data-mce-placeholder="1" class="mce-object" width="20" height="20" alt="&lt;script&gt;" title="&lt;script&gt;" />
<img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" data-wp-preserve="%3Cscript%20src%3D%22https%3A%2F%2Fmaxcdn.bootstrapcdn.com%2Fbootstrap%2F3.3.7%2Fjs%2Fbootstrap.min.js%22%3E%3C%2Fscript%3E" data-mce-resize="false" data-mce-placeholder="1" class="mce-object" width="20" height="20" alt="&lt;script&gt;" title="&lt;script&gt;" />
</head>
 
<body class = "bg-info">
 
 
<div align="center">
<!-- Inserting the image -->
<img src="/static/edurekaLogo.png" alt="Edureka Logo">
</div>
 
 
 
 
<div class="row">
 
 
<div class="col-md-6 offset-md-3" style="background-color: #fff; margin-top: 40px; padding:20px;">
<!-- retrieving HTML String from the child Views -->
{{{body}}}
</div>
 
 
</div>
 
 
</body>
</html>

Finally, inside the course folder, we will be creating two child views, one of which will be used for course addition or update and the second view will display the complete list of the available courses. Let’s first focus on the first view i.e courseAddEdit.hbs which will look like the below screenshot.
How to Build CRUD Application using Node.js and MongoDB

So, let me now show, how to build this view.

As you can see in the screenshot, the page will be containing four input fields and two buttons. One button will be submitting details filled in by the user into the database and the second button will display the complete list of courses available in the database. In order to make sure that the inputs are correct, you need to add some validations as well. Once done, you will be able to see this view using ‘/course’ URL. Below is the code, you will be needing to create courseAddEdit.hbs file:

courseAddEdit.hbs

<!-- Obtaining value from the course controller -->
 
<h3>{{viewTitle}}</h3>
<form action="/course" method="POST">
<input type="hidden" name="_id" value="{{course._id}}">
 
<div class = "form-group">
<label>Course Name</label>
<input type="text" maxlength="100" class="form-control" name="courseName" placeholder="Course Name" value="{{course.courseName}}">
 
<div class="text-danger">
{{course.courseNameError}}</div>
</div>
<div class = "form-group">
<label>Course ID</label>
<input type="number" min='10000' max='99999' class="form-control" name="courseId" placeholder="Course Id" value="{{course.courseId}} " required>
</div>
<div class = "form-row">
<div class = "form-group col-md-6">
<label>Course Duration</label>
<input type="number" min='10' max='99' class="form-control" name="courseDuration" placeholder="Course Duration (Hrs)" "{{course.courseDuration}} " required>
</div>
<div class = "form-group col-md-6">
<label>Course Fee</label>
<input type="number" min='100' max="100000" class="form-control" name="courseFee" placeholder="Course Fee (USD)" "{{course.courseFee}} " required>
</div>
</div>
<div class="form-group">
<button type="submit" class="btn btn-info"><i class="fa fa-database"></i> Submit</button>
<a class="btn btn-secondary" href="/course/list"><i class="fa fa-list-alt"></i> View All Courses</a>
</div>
</form>

Now, let me show you the next view i.e list.hbs, which will retrieve the complete list of available courses from the database and display them on your screen:
How to Build CRUD Application using Node.js and MongoDB

In this view, I am using a table to display the list of courses. This table will have five columns where the first four will display the course details while the last column will enable you to edit/delete a record directly from the application interface. The controllers of these functions have been already created in the script.js file. So, the only thing left is to add the view and in order to do so create a list.hbs file and type in the below-written code.

list.hbs

<div>
<a class="btn btn-secondary" href="/course"><i class="fa fa-plus"></i> Create New</a> 
 
<h3 align="center">Edureka's Course List</h3>
</div>
<table class="table table-striped">
<thead>
<tr>
<th>Course Name</th>
<th>Course Id</th>
<th>Course Duration(Hrs)</th>
<th>Course Fee(USD)</th>
<th></th>
</tr>
</thead>
<tbody>
{{#each list}}
<tr align="center">
<td>{{this.courseName}}</td>
<td>{{this.courseId}}</td>
<td>{{this.courseDuration}}</td>
<td>{{this.courseFee}}</td>
<td>
<a href="/course/{{this._id}}"> Edit </a>
<a href="/course/delete/{{this._id}}" onclick="return confirm('Are you sure to delete this record ?');"> Delete </a>
</td>
</tr>
{{/each}}
</tbody>
</table>

This concludes are the coding part, now it’s time to test our application. For that, open the command prompt and navigate to the project folder or if you are using an IDE open the terminal and type in the below command to start the server.

nodemon script.js

Now you can launch your application in any browser at http://localhost:8080.

Once you have added your own data, you can go back in MongoDB and check whether the data has been added there or not. If you refer the below screenshot, you will see all my data has been successfully added. Which means my MongoDB is connected and working perfectly with my Node.js API.
With this, we come to an end of this Node.js MongoDB Tutorial. Hope I was able to keep the concepts clear and helped you in understanding how exactly MongoDB works with Node.js.

#Nodejs #MongoDB #WebDev #Databases

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Nbb requires Node.js v12 or newer.

How does this tool work?

CLJS code is evaluated through SCI, the same interpreter that powers babashka. Because SCI works with advanced compilation, the bundle size, especially when combined with other dependencies, is smaller than what you get with self-hosted CLJS. That makes startup faster. The trade-off is that execution is less performant and that only a subset of CLJS is available (e.g. no deftype, yet).

Usage

Install nbb from NPM:

$ npm install nbb -g

Omit -g for a local install.

Try out an expression:

$ nbb -e '(+ 1 2 3)'
6

And then install some other NPM libraries to use in the script. E.g.:

$ npm install csv-parse shelljs zx

Create a script which uses the NPM libraries:

(ns script
  (:require ["csv-parse/lib/sync$default" :as csv-parse]
            ["fs" :as fs]
            ["path" :as path]
            ["shelljs$default" :as sh]
            ["term-size$default" :as term-size]
            ["zx$default" :as zx]
            ["zx$fs" :as zxfs]
            [nbb.core :refer [*file*]]))

(prn (path/resolve "."))

(prn (term-size))

(println (count (str (fs/readFileSync *file*))))

(prn (sh/ls "."))

(prn (csv-parse "foo,bar"))

(prn (zxfs/existsSync *file*))

(zx/$ #js ["ls"])

Call the script:

$ nbb script.cljs
"/private/tmp/test-script"
#js {:columns 216, :rows 47}
510
#js ["node_modules" "package-lock.json" "package.json" "script.cljs"]
#js [#js ["foo" "bar"]]
true
$ ls
node_modules
package-lock.json
package.json
script.cljs

Macros

Nbb has first class support for macros: you can define them right inside your .cljs file, like you are used to from JVM Clojure. Consider the plet macro to make working with promises more palatable:

(defmacro plet
  [bindings & body]
  (let [binding-pairs (reverse (partition 2 bindings))
        body (cons 'do body)]
    (reduce (fn [body [sym expr]]
              (let [expr (list '.resolve 'js/Promise expr)]
                (list '.then expr (list 'clojure.core/fn (vector sym)
                                        body))))
            body
            binding-pairs)))

Using this macro we can look async code more like sync code. Consider this puppeteer example:

(-> (.launch puppeteer)
      (.then (fn [browser]
               (-> (.newPage browser)
                   (.then (fn [page]
                            (-> (.goto page "https://clojure.org")
                                (.then #(.screenshot page #js{:path "screenshot.png"}))
                                (.catch #(js/console.log %))
                                (.then #(.close browser)))))))))

Using plet this becomes:

(plet [browser (.launch puppeteer)
       page (.newPage browser)
       _ (.goto page "https://clojure.org")
       _ (-> (.screenshot page #js{:path "screenshot.png"})
             (.catch #(js/console.log %)))]
      (.close browser))

See the puppeteer example for the full code.

Since v0.0.36, nbb includes promesa which is a library to deal with promises. The above plet macro is similar to promesa.core/let.

Startup time

$ time nbb -e '(+ 1 2 3)'
6
nbb -e '(+ 1 2 3)'   0.17s  user 0.02s system 109% cpu 0.168 total

The baseline startup time for a script is about 170ms seconds on my laptop. When invoked via npx this adds another 300ms or so, so for faster startup, either use a globally installed nbb or use $(npm bin)/nbb script.cljs to bypass npx.

Dependencies

NPM dependencies

Nbb does not depend on any NPM dependencies. All NPM libraries loaded by a script are resolved relative to that script. When using the Reagent module, React is resolved in the same way as any other NPM library.

Classpath

To load .cljs files from local paths or dependencies, you can use the --classpath argument. The current dir is added to the classpath automatically. So if there is a file foo/bar.cljs relative to your current dir, then you can load it via (:require [foo.bar :as fb]). Note that nbb uses the same naming conventions for namespaces and directories as other Clojure tools: foo-bar in the namespace name becomes foo_bar in the directory name.

To load dependencies from the Clojure ecosystem, you can use the Clojure CLI or babashka to download them and produce a classpath:

$ classpath="$(clojure -A:nbb -Spath -Sdeps '{:aliases {:nbb {:replace-deps {com.github.seancorfield/honeysql {:git/tag "v2.0.0-rc5" :git/sha "01c3a55"}}}}}')"

and then feed it to the --classpath argument:

$ nbb --classpath "$classpath" -e "(require '[honey.sql :as sql]) (sql/format {:select :foo :from :bar :where [:= :baz 2]})"
["SELECT foo FROM bar WHERE baz = ?" 2]

Currently nbb only reads from directories, not jar files, so you are encouraged to use git libs. Support for .jar files will be added later.

Current file

The name of the file that is currently being executed is available via nbb.core/*file* or on the metadata of vars:

(ns foo
  (:require [nbb.core :refer [*file*]]))

(prn *file*) ;; "/private/tmp/foo.cljs"

(defn f [])
(prn (:file (meta #'f))) ;; "/private/tmp/foo.cljs"

Reagent

Nbb includes reagent.core which will be lazily loaded when required. You can use this together with ink to create a TUI application:

$ npm install ink

ink-demo.cljs:

(ns ink-demo
  (:require ["ink" :refer [render Text]]
            [reagent.core :as r]))

(defonce state (r/atom 0))

(doseq [n (range 1 11)]
  (js/setTimeout #(swap! state inc) (* n 500)))

(defn hello []
  [:> Text {:color "green"} "Hello, world! " @state])

(render (r/as-element [hello]))

Promesa

Working with callbacks and promises can become tedious. Since nbb v0.0.36 the promesa.core namespace is included with the let and do! macros. An example:

(ns prom
  (:require [promesa.core :as p]))

(defn sleep [ms]
  (js/Promise.
   (fn [resolve _]
     (js/setTimeout resolve ms))))

(defn do-stuff
  []
  (p/do!
   (println "Doing stuff which takes a while")
   (sleep 1000)
   1))

(p/let [a (do-stuff)
        b (inc a)
        c (do-stuff)
        d (+ b c)]
  (prn d))
$ nbb prom.cljs
Doing stuff which takes a while
Doing stuff which takes a while
3

Also see API docs.

Js-interop

Since nbb v0.0.75 applied-science/js-interop is available:

(ns example
  (:require [applied-science.js-interop :as j]))

(def o (j/lit {:a 1 :b 2 :c {:d 1}}))

(prn (j/select-keys o [:a :b])) ;; #js {:a 1, :b 2}
(prn (j/get-in o [:c :d])) ;; 1

Most of this library is supported in nbb, except the following:

  • destructuring using :syms
  • property access using .-x notation. In nbb, you must use keywords.

See the example of what is currently supported.

Examples

See the examples directory for small examples.

Also check out these projects built with nbb:

API

See API documentation.

Migrating to shadow-cljs

See this gist on how to convert an nbb script or project to shadow-cljs.

Build

Prequisites:

  • babashka >= 0.4.0
  • Clojure CLI >= 1.10.3.933
  • Node.js 16.5.0 (lower version may work, but this is the one I used to build)

To build:

  • Clone and cd into this repo
  • bb release

Run bb tasks for more project-related tasks.

Download Details:
Author: borkdude
Download Link: Download The Source Code
Official Website: https://github.com/borkdude/nbb 
License: EPL-1.0

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Why use Node.js for Web Development? Benefits and Examples of Apps

Front-end web development has been overwhelmed by JavaScript highlights for quite a long time. Google, Facebook, Wikipedia, and most of all online pages use JS for customer side activities. As of late, it additionally made a shift to cross-platform mobile development as a main technology in React Native, Nativescript, Apache Cordova, and other crossover devices. 

Throughout the most recent couple of years, Node.js moved to backend development as well. Designers need to utilize a similar tech stack for the whole web project without learning another language for server-side development. Node.js is a device that adjusts JS usefulness and syntax to the backend. 

What is Node.js? 

Node.js isn’t a language, or library, or system. It’s a runtime situation: commonly JavaScript needs a program to work, however Node.js makes appropriate settings for JS to run outside of the program. It’s based on a JavaScript V8 motor that can run in Chrome, different programs, or independently. 

The extent of V8 is to change JS program situated code into machine code — so JS turns into a broadly useful language and can be perceived by servers. This is one of the advantages of utilizing Node.js in web application development: it expands the usefulness of JavaScript, permitting designers to coordinate the language with APIs, different languages, and outside libraries.

What Are the Advantages of Node.js Web Application Development? 

Of late, organizations have been effectively changing from their backend tech stacks to Node.js. LinkedIn picked Node.js over Ruby on Rails since it took care of expanding responsibility better and decreased the quantity of servers by multiple times. PayPal and Netflix did something comparative, just they had a goal to change their design to microservices. We should investigate the motivations to pick Node.JS for web application development and when we are planning to hire node js developers. 

Amazing Tech Stack for Web Development 

The principal thing that makes Node.js a go-to environment for web development is its JavaScript legacy. It’s the most well known language right now with a great many free devices and a functioning local area. Node.js, because of its association with JS, immediately rose in ubiquity — presently it has in excess of 368 million downloads and a great many free tools in the bundle module. 

Alongside prevalence, Node.js additionally acquired the fundamental JS benefits: 

  • quick execution and information preparing; 
  • exceptionally reusable code; 
  • the code is not difficult to learn, compose, read, and keep up; 
  • tremendous asset library, a huge number of free aides, and a functioning local area. 

In addition, it’s a piece of a well known MEAN tech stack (the blend of MongoDB, Express.js, Angular, and Node.js — four tools that handle all vital parts of web application development). 

Designers Can Utilize JavaScript for the Whole Undertaking 

This is perhaps the most clear advantage of Node.js web application development. JavaScript is an unquestionable requirement for web development. Regardless of whether you construct a multi-page or single-page application, you need to know JS well. On the off chance that you are now OK with JavaScript, learning Node.js won’t be an issue. Grammar, fundamental usefulness, primary standards — every one of these things are comparable. 

In the event that you have JS designers in your group, it will be simpler for them to learn JS-based Node than a totally new dialect. What’s more, the front-end and back-end codebase will be basically the same, simple to peruse, and keep up — in light of the fact that they are both JS-based. 

A Quick Environment for Microservice Development 

There’s another motivation behind why Node.js got famous so rapidly. The environment suits well the idea of microservice development (spilling stone monument usefulness into handfuls or many more modest administrations). 

Microservices need to speak with one another rapidly — and Node.js is probably the quickest device in information handling. Among the fundamental Node.js benefits for programming development are its non-obstructing algorithms.

Node.js measures a few demands all at once without trusting that the first will be concluded. Many microservices can send messages to one another, and they will be gotten and addressed all the while. 

Versatile Web Application Development 

Node.js was worked in view of adaptability — its name really says it. The environment permits numerous hubs to run all the while and speak with one another. Here’s the reason Node.js adaptability is better than other web backend development arrangements. 

Node.js has a module that is liable for load adjusting for each running CPU center. This is one of numerous Node.js module benefits: you can run various hubs all at once, and the environment will naturally adjust the responsibility. 

Node.js permits even apportioning: you can part your application into various situations. You show various forms of the application to different clients, in light of their age, interests, area, language, and so on. This builds personalization and diminishes responsibility. Hub accomplishes this with kid measures — tasks that rapidly speak with one another and share a similar root. 

What’s more, Node’s non-hindering solicitation handling framework adds to fast, letting applications measure a great many solicitations. 

Control Stream Highlights

Numerous designers consider nonconcurrent to be one of the two impediments and benefits of Node.js web application development. In Node, at whatever point the capacity is executed, the code consequently sends a callback. As the quantity of capacities develops, so does the number of callbacks — and you end up in a circumstance known as the callback damnation. 

In any case, Node.js offers an exit plan. You can utilize systems that will plan capacities and sort through callbacks. Systems will associate comparable capacities consequently — so you can track down an essential component via search or in an envelope. At that point, there’s no compelling reason to look through callbacks.

 

Final Words

So, these are some of the top benefits of Nodejs in web application development. This is how Nodejs is contributing a lot to the field of web application development. 

I hope now you are totally aware of the whole process of how Nodejs is really important for your web project. If you are looking to hire a node js development company in India then I would suggest that you take a little consultancy too whenever you call. 

Good Luck!

Original Source

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Hire Dedicated Node.js Developers - Hire Node.js Developers

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Top 10 NodeJs app Development Companies- ValueCoders

Node.js is a prominent tech trend in the space of web and mobile application development. It has been proven very efficient and useful for a variety of application development. Thus, all business owners are eager to leverage this technology for creating their applications.

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Before enlisting companies, I would like to say that every company has a foundation on which they thrive. Their end goals, qualities, and excellence define their competence. Thus, I prepared this list by considering a number of aspects. While making this list, I have considered the following aspects:

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I believe this list will help you out in choosing the best NodeJS service provider company. So, now let’s explore the top NodeJS developer companies to choose from in 2021.

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If you want to hire NodeJS developers to secure an outstanding application, I would definitely suggest them. They serve in the area of eLearning, FinTech, eCommerce, Telecommunications, Mobile Device Management, and more.

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