Build and Run a Node.js App with Docker

Introduction

The Docker platform allows developers to package and run applications as containers. A container is an isolated process that runs on a shared operating system, offering a lighter weight alternative to virtual machines. Though containers are not new, they offer benefits — including process isolation and environment standardization — that are growing in importance as more developers use distributed application architectures.

When building and scaling an application with Docker, the starting point is typically creating an image for your application, which you can then run in a container. The image includes your application code, libraries, configuration files, environment variables, and runtime. Using an image ensures that the environment in your container is standardized and contains only what is necessary to build and run your application.

In this tutorial, you will create an application image for a static website that uses the Express framework and Bootstrap. You will then build a container using that image and push it to Docker Hub for future use. Finally, you will pull the stored image from your Docker Hub repository and build another container, demonstrating how you can recreate and scale your application.

Step 1 — Installing Your Application Dependencies

To create your image, you will first need to make your application files, which you can then copy to your container. These files will include your application’s static content, code, and dependencies.

First, create a directory for your project in your non-root user’s home directory. We will call ours node_project, but you should feel free to replace this with something else:

mkdir node_project

Navigate to this directory:

cd node_project

This will be the root directory of the project.

Next, create a package.json file with your project’s dependencies and other identifying information. Open the file with nano or your favorite editor:

nano package.json

Add the following information about the project, including its name, author, license, entrypoint, and dependencies. Be sure to replace the author information with your own name and contact details:

~/node_project/package.json

{
  "name": "nodejs-image-demo",
  "version": "1.0.0",
  "description": "nodejs image demo",
  "author": "Sammy the Shark <sammy@example.com>",
  "license": "MIT",
  "main": "app.js",
  "keywords": [
    "nodejs",
    "bootstrap",
    "express"
  ],
  "dependencies": {
    "express": "^4.16.4"
  }
}

This file includes the project name, author, and license under which it is being shared. Npm recommends making your project name short and descriptive, and avoiding duplicates in the npm registry. We’ve listed the MIT license in the license field, permitting the free use and distribution of the application code.

Additionally, the file specifies:

  • "main": The entrypoint for the application, app.js. You will create this file next.
  • "dependencies": The project dependencies — in this case, Express 4.16.4 or above.

Though this file does not list a repository, you can add one by following these guidelines on adding a repository to your package.json file. This is a good addition if you are versioning your application.

Save and close the file when you’ve finished making changes.

To install your project’s dependencies, run the following command:

npm install

This will install the packages you’ve listed in your package.json file in your project directory.

We can now move on to building the application files.

Step 2 — Creating the Application Files

We will create a website that offers users information about sharks. Our application will have a main entrypoint, app.js, and a views directory that will include the project’s static assets. The landing page, index.html, will offer users some preliminary information and a link to a page with more detailed shark information, sharks.html. In the views directory, we will create both the landing page and sharks.html.

First, open app.js in the main project directory to define the project’s routes:

nano app.js

The first part of the file will create the Express application and Router objects, and define the base directory and port as constants:

~/node_project/app.js

const express = require('express');
const app = express();
const router = express.Router();

const path = __dirname + '/views/';
const port = 8080;

The require function loads the express module, which we then use to create the app and router objects. The router object will perform the routing function of the application, and as we define HTTP method routes we will add them to this object to define how our application will handle requests.

This section of the file also sets a couple of constants, path and port:

  • path: Defines the base directory, which will be the views subdirectory within the current project directory.
  • port: Tells the app to listen on and bind to port 8080.

Next, set the routes for the application using the router object:

~/node_project/app.js

...

router.use(function (req,res,next) {
  console.log('/' + req.method);
  next();
});

router.get('/', function(req,res){
  res.sendFile(path + 'index.html');
});

router.get('/sharks', function(req,res){
  res.sendFile(path + 'sharks.html');
});

The router.use function loads a middleware function that will log the router’s requests and pass them on to the application’s routes. These are defined in the subsequent functions, which specify that a GET request to the base project URL should return the index.html page, while a GET request to the /sharks route should return sharks.html.

Finally, mount the router middleware and the application’s static assets and tell the app to listen on port 8080:

~/node_project/app.js

...

app.use(express.static(path));
app.use('/', router);

app.listen(port, function () {
  console.log('Example app listening on port 8080!')
})

The finished app.js file will look like this:

~/node_project/app.js

const express = require('express');
const app = express();
const router = express.Router();

const path = __dirname + '/views/';
const port = 8080;

router.use(function (req,res,next) {
  console.log('/' + req.method);
  next();
});

router.get('/', function(req,res){
  res.sendFile(path + 'index.html');
});

router.get('/sharks', function(req,res){
  res.sendFile(path + 'sharks.html');
});

app.use(express.static(path));
app.use('/', router);

app.listen(port, function () {
  console.log('Example app listening on port 8080!')
})

Save and close the file when you are finished.

Next, let’s add some static content to the application. Start by creating the views directory:

mkdir views

Open the landing page file, index.html:

nano views/index.html

Add the following code to the file, which will import Boostrap and create a jumbotron component with a link to the more detailed sharks.html info page:

~/node_project/views/index.html

<!DOCTYPE html>
<html lang="en">

<head>
    <title>About Sharks</title>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css" integrity="sha384-MCw98/SFnGE8fJT3GXwEOngsV7Zt27NXFoaoApmYm81iuXoPkFOJwJ8ERdknLPMO" crossorigin="anonymous">
    <link href="css/styles.css" rel="stylesheet">
    <link href="https://fonts.googleapis.com/css?family=Merriweather:400,700" rel="stylesheet" type="text/css">
</head>

<body>
    <nav class="navbar navbar-dark bg-dark navbar-static-top navbar-expand-md">
        <div class="container">
            <button type="button" class="navbar-toggler collapsed" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1" aria-expanded="false">  Toggle navigation
            </button> <a class="navbar-brand" href="#">Everything Sharks</a>
            <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
                <ul class="nav navbar-nav mr-auto">
                    <li class="active nav-item"><a href="/" class="nav-link">Home</a>
                    </li>
                    <li class="nav-item"><a href="/sharks" class="nav-link">Sharks</a>
                    </li>
                </ul>
            </div>
        </div>
    </nav>
    <div class="jumbotron">
        <div class="container">
            <h1>Want to Learn About Sharks?</h1>
            <p>Are you ready to learn about sharks?</p>
            <br>
            <p><a class="btn btn-primary btn-lg" href="/sharks" role="button">Get Shark Info</a>
            </p>
        </div>
    </div>
    <div class="container">
        <div class="row">
            <div class="col-lg-6">
                <h3>Not all sharks are alike</h3>
                <p>Though some are dangerous, sharks generally do not attack humans. Out of the 500 species known to researchers, only 30 have been known to attack humans.
                </p>
            </div>
            <div class="col-lg-6">
                <h3>Sharks are ancient</h3>
                <p>There is evidence to suggest that sharks lived up to 400 million years ago.
                </p>
            </div>
        </div>
    </div>
</body>

</html>

The top-level navbar here allows users to toggle between the Home and Sharks pages. In the navbar-nav subcomponent, we are using Bootstrap’s active class to indicate the current page to the user. We’ve also specified the routes to our static pages, which match the routes we defined in app.js:

~/node_project/views/index.html

...
<div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
   <ul class="nav navbar-nav mr-auto">
      <li class="active nav-item"><a href="/" class="nav-link">Home</a>
      </li>
      <li class="nav-item"><a href="/sharks" class="nav-link">Sharks</a>
      </li>
   </ul>
</div>
...

Additionally, we’ve created a link to our shark information page in our jumbotron’s button:

~/node_project/views/index.html

...
<div class="jumbotron">
   <div class="container">
      <h1>Want to Learn About Sharks?</h1>
      <p>Are you ready to learn about sharks?</p>
      <br>
      <p><a class="btn btn-primary btn-lg" href="/sharks" role="button">Get Shark Info</a>
      </p>
   </div>
</div>
...

There is also a link to a custom style sheet in the header:

~/node_project/views/index.html

...
<link href="css/styles.css" rel="stylesheet">
...

We will create this style sheet at the end of this step.

Save and close the file when you are finished.

With the application landing page in place, we can create our shark information page, sharks.html, which will offer interested users more information about sharks.

Open the file:

nano views/sharks.html

Add the following code, which imports Bootstrap and the custom style sheet and offers users detailed information about certain sharks:

~/node_project/views/sharks.html

<!DOCTYPE html>
<html lang="en">

<head>
    <title>About Sharks</title>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css" integrity="sha384-MCw98/SFnGE8fJT3GXwEOngsV7Zt27NXFoaoApmYm81iuXoPkFOJwJ8ERdknLPMO" crossorigin="anonymous">
    <link href="css/styles.css" rel="stylesheet">
    <link href="https://fonts.googleapis.com/css?family=Merriweather:400,700" rel="stylesheet" type="text/css">
</head>
<nav class="navbar navbar-dark bg-dark navbar-static-top navbar-expand-md">
    <div class="container">
        <button type="button" class="navbar-toggler collapsed" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1" aria-expanded="false">  Toggle navigation
        </button> <a class="navbar-brand" href="/">Everything Sharks</a>
        <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
            <ul class="nav navbar-nav mr-auto">
                <li class="nav-item"><a href="/" class="nav-link">Home</a>
                </li>
                <li class="active nav-item"><a href="/sharks" class="nav-link">Sharks</a>
                </li>
            </ul>
        </div>
    </div>
</nav>
<div class="jumbotron text-center">
    <h1>Shark Info</h1>
</div>
<div class="container">
    <div class="row">
        <div class="col-lg-6">
            <p>
                <div class="caption">Some sharks are known to be dangerous to humans, though many more are not. The sawshark, for example, is not considered a threat to humans.
                </div>
                <img src="https://assets.digitalocean.com/articles/docker_node_image/sawshark.jpg" alt="Sawshark">
            </p>
        </div>
        <div class="col-lg-6">
            <p>
                <div class="caption">Other sharks are known to be friendly and welcoming!</div>
                <img src="https://assets.digitalocean.com/articles/docker_node_image/sammy.png" alt="Sammy the Shark">
            </p>
        </div>
    </div>
</div>

</html>

Note that in this file, we again use the active class to indicate the current page.

Save and close the file when you are finished.

Finally, create the custom CSS style sheet that you’ve linked to in index.html and sharks.html by first creating a css folder in the views directory:

mkdir views/css

Open the style sheet:

nano views/css/styles.css

Add the following code, which will set the desired color and font for our pages:

~/node_project/views/css/styles.css

.navbar {
    margin-bottom: 0;
}

body {
    background: #020A1B;
    color: #ffffff;
    font-family: 'Merriweather', sans-serif;
}

h1,
h2 {
    font-weight: bold;
}

p {
    font-size: 16px;
    color: #ffffff;
}

.jumbotron {
    background: #0048CD;
    color: white;
    text-align: center;
}

.jumbotron p {
    color: white;
    font-size: 26px;
}

.btn-primary {
    color: #fff;
    text-color: #000000;
    border-color: white;
    margin-bottom: 5px;
}

img,
video,
audio {
    margin-top: 20px;
    max-width: 80%;
}

div.caption: {
    float: left;
    clear: both;
}

In addition to setting font and color, this file also limits the size of the images by specifying a max-width of 80%. This will prevent them from taking up more room than we would like on the page.

Save and close the file when you are finished.

With the application files in place and the project dependencies installed, you are ready to start the application.

If you followed the initial server setup tutorial in the prerequisites, you will have an active firewall permitting only SSH traffic. To permit traffic to port 8080 run:

sudo ufw allow 8080

To start the application, make sure that you are in your project’s root directory:

cd ~/node_project

Start the application with node app.js:

node app.js

Navigate your browser to http://``your_server_ip``:8080. You will see the following landing page:

Application Landing Page

Click on the Get Shark Info button. You will see the following information page:

Shark Info Page

You now have an application up and running. When you are ready, quit the server by typing CTRL+C. We can now move on to creating the Dockerfile that will allow us to recreate and scale this application as desired.

Step 3 — Writing the Dockerfile

Your Dockerfile specifies what will be included in your application container when it is executed. Using a Dockerfile allows you to define your container environment and avoid discrepancies with dependencies or runtime versions.

Following these guidelines on building optimized containers, we will make our image as efficient as possible by minimizing the number of image layers and restricting the image’s function to a single purpose — recreating our application files and static content.

In your project’s root directory, create the Dockerfile:

nano Dockerfile

Docker images are created using a succession of layered images that build on one another. Our first step will be to add the base image for our application that will form the starting point of the application build.

Let’s use the node: 10-alpine image, since at the time of writing this is the recommended LTS version of Node.js. The alpine image is derived from the Alpine Linux project, and will help us keep our image size down. For more information about whether or not the alpine image is the right choice for your project, please see the full discussion under the Image Variants section of the Docker Hub Node image page.

Add the following FROM instruction to set the application’s base image:

~/node_project/Dockerfile

FROM node:10-alpine

This image includes Node.js and npm. Each Dockerfile must begin with a FROM instruction.

By default, the Docker Node image includes a non-root node user that you can use to avoid running your application container as root. It is a recommended security practice to avoid running containers as root and to restrict capabilities within the container to only those required to run its processes. We will therefore use the node user’s home directory as the working directory for our application and set them as our user inside the container. For more information about best practices when working with the Docker Node image, see this best practices guide.

To fine-tune the permissions on our application code in the container, let’s create the node_modules subdirectory in /home/node along with the app directory. Creating these directories will ensure that they have the permissions we want, which will be important when we create local node modules in the container with npm install. In addition to creating these directories, we will set ownership on them to our node user:

~/node_project/Dockerfile

...
RUN mkdir -p /home/node/app/node_modules && chown -R node:node /home/node/app

For more information on the utility of consolidating RUN instructions, see this discussion of how to manage container layers.

Next, set the working directory of the application to /home/node/app:

~/node_project/Dockerfile

...
WORKDIR /home/node/app

If a WORKDIR isn’t set, Docker will create one by default, so it’s a good idea to set it explicitly.

Next, copy the package.json and package-lock.json (for npm 5+) files:

~/node_project/Dockerfile

...
COPY package*.json ./

Adding this COPY instruction before running npm install or copying the application code allows us to take advantage of Docker’s caching mechanism. At each stage in the build, Docker will check to see if it has a layer cached for that particular instruction. If we change package.json, this layer will be rebuilt, but if we don’t, this instruction will allow Docker to use the existing image layer and skip reinstalling our node modules.

To ensure that all of the application files are owned by the non-root node user, including the contents of the node_modules directory, switch the user to node before running npm install:

~/node_project/Dockerfile

...
USER node

After copying the project dependencies and switching our user, we can run npm install:

~/node_project/Dockerfile

...
RUN npm install

Next, copy your application code with the appropriate permissions to the application directory on the container:

~/node_project/Dockerfile

...
COPY --chown=node:node . .

This will ensure that the application files are owned by the non-root node user.

Finally, expose port 8080 on the container and start the application:

~/node_project/Dockerfile

...
EXPOSE 8080

CMD [ "node", "app.js" ]

EXPOSE does not publish the port, but instead functions as a way of documenting which ports on the container will be published at runtime. CMD runs the command to start the application — in this case, node app.js. Note that there should only be one CMD instruction in each Dockerfile. If you include more than one, only the last will take effect.

There are many things you can do with the Dockerfile. For a complete list of instructions, please refer to Docker’s Dockerfile reference documentation.

The complete Dockerfile looks like this:

~/node_project/Dockerfile

FROM node:10-alpine

RUN mkdir -p /home/node/app/node_modules && chown -R node:node /home/node/app

WORKDIR /home/node/app

COPY package*.json ./

USER node

RUN npm install

COPY --chown=node:node . .

EXPOSE 8080

CMD [ "node", "app.js" ]

Save and close the file when you are finished editing.

Before building the application image, let’s add a .dockerignore[ file](https://docs.docker.com/engine/reference/builder/#dockerignore-file). Working in a similar way to a .gitignore file.dockerignore specifies which files and directories in your project directory should not be copied over to your container.

Open the .dockerignore file:

nano .dockerignore

Inside the file, add your local node modules, npm logs, Dockerfile, and .dockerignore file:

~/node_project/.dockerignore

node_modules
npm-debug.log
Dockerfile
.dockerignore

If you are working with Git then you will also want to add your .git directory and .gitignore file.

Save and close the file when you are finished.

You are now ready to build the application image using the docker build command. Using the -t flag with docker build will allow you to tag the image with a memorable name. Because we are going to push the image to Docker Hub, let’s include our Docker Hub username in the tag. We will tag the image as nodejs-image-demo, but feel free to replace this with a name of your own choosing. Remember to also replace your_dockerhub_username with your own Docker Hub username:

docker build -t your_dockerhub_username/nodejs-image-demo .

The . specifies that the build context is the current directory.

It will take a minute or two to build the image. Once it is complete, check your images:

docker images

You will see the following output:

Output

REPOSITORY                                         TAG                 IMAGE ID            CREATED             SIZE
your_dockerhub_username/nodejs-image-demo          latest              1c723fb2ef12        8 seconds ago       73MB
node                                               10-alpine           f09e7c96b6de        3 weeks ago        70.7MB

It is now possible to create a container with this image using docker run. We will include three flags with this command:

  • -p: This publishes the port on the container and maps it to a port on our host. We will use port 80 on the host, but you should feel free to modify this as necessary if you have another process running on that port. For more information about how this works, see this discussion in the Docker docs on port binding.
  • -d: This runs the container in the background.
  • --name: This allows us to give the container a memorable name.

Run the following command to build the container:

docker run --name nodejs-image-demo -p 80:8080 -d your_dockerhub_username/nodejs-image-demo

Once your container is up and running, you can inspect a list of your running containers with docker ps:

docker ps

You will see the following output:

Output

CONTAINER ID        IMAGE                                                   COMMAND             CREATED             STATUS              PORTS                  NAMES
e50ad27074a7        your_dockerhub_username/nodejs-image-demo               "node app.js"       8 seconds ago       Up 7 seconds        0.0.0.0:80->8080/tcp   nodejs-image-demo

With your container running, you can now visit your application by navigating your browser to http://``your_server_ip. You will see your application landing page once again:

Application Landing Page

Now that you have created an image for your application, you can push it to Docker Hub for future use.

Step 4 — Using a Repository to Work with Images

By pushing your application image to a registry like Docker Hub, you make it available for subsequent use as you build and scale your containers. We will demonstrate how this works by pushing the application image to a repository and then using the image to recreate our container.

The first step to pushing the image is to log in to the Docker Hub account you created in the prerequisites:

docker login -u your_dockerhub_username

When prompted, enter your Docker Hub account password. Logging in this way will create a ~/.docker/config.json file in your user’s home directory with your Docker Hub credentials.

You can now push the application image to Docker Hub using the tag you created earlier, your_dockerhub_username``/``nodejs-image-demo:

docker push your_dockerhub_username/nodejs-image-demo

Let’s test the utility of the image registry by destroying our current application container and image and rebuilding them with the image in our repository.

First, list your running containers:

docker ps

You will see the following output:

Output

CONTAINER ID        IMAGE                                       COMMAND             CREATED             STATUS              PORTS                  NAMES
e50ad27074a7        your_dockerhub_username/nodejs-image-demo   "node app.js"       3 minutes ago       Up 3 minutes        0.0.0.0:80->8080/tcp   nodejs-image-demo

Using the CONTAINER ID listed in your output, stop the running application container. Be sure to replace the highlighted ID below with your own CONTAINER ID:

docker stop e50ad27074a7

List your all of your images with the -a flag:

docker images -a

You will see the following output with the name of your image, your_dockerhub_username``/``nodejs-image-demo, along with the node image and the other images from your build:

Output

REPOSITORY                                           TAG                 IMAGE ID            CREATED             SIZE
your_dockerhub_username/nodejs-image-demo            latest              1c723fb2ef12        7 minutes ago       73MB
<none>                                               <none>              2e3267d9ac02        4 minutes ago       72.9MB
<none>                                               <none>              8352b41730b9        4 minutes ago       73MB
<none>                                               <none>              5d58b92823cb        4 minutes ago       73MB
<none>                                               <none>              3f1e35d7062a        4 minutes ago       73MB
<none>                                               <none>              02176311e4d0        4 minutes ago       73MB
<none>                                               <none>              8e84b33edcda        4 minutes ago       70.7MB
<none>                                               <none>              6a5ed70f86f2        4 minutes ago       70.7MB
<none>                                               <none>              776b2637d3c1        4 minutes ago       70.7MB
node                                                 10-alpine           f09e7c96b6de        3 weeks ago         70.7MB

Remove the stopped container and all of the images, including unused or dangling images, with the following command:

docker system prune -a

Type y when prompted in the output to confirm that you would like to remove the stopped container and images. Be advised that this will also remove your build cache.

You have now removed both the container running your application image and the image itself. For more information on removing Docker containers, images, and volumes, please see How To Remove Docker Images, Containers, and Volumes.

With all of your images and containers deleted, you can now pull the application image from Docker Hub:

docker pull your_dockerhub_username/nodejs-image-demo

List your images once again:

docker images

You will see your application image:

Output

REPOSITORY                                     TAG                 IMAGE ID            CREATED             SIZE
your_dockerhub_username/nodejs-image-demo      latest              1c723fb2ef12        11 minutes ago      73MB

You can now rebuild your container using the command from Step 3:

docker run --name nodejs-image-demo -p 80:8080 -d your_dockerhub_username/nodejs-image-demo

List your running containers:

docker ps
Output

CONTAINER ID        IMAGE                                                   COMMAND             CREATED             STATUS              PORTS                  NAMES
f6bc2f50dff6        your_dockerhub_username/nodejs-image-demo               "node app.js"       4 seconds ago       Up 3 seconds        0.0.0.0:80->8080/tcp   nodejs-image-demo

Visit http://``your_server_ip once again to view your running application.

Conclusion

In this tutorial you created a static web application with Express and Bootstrap, as well as a Docker image for this application. You used this image to create a container and pushed the image to Docker Hub. From there, you were able to destroy your image and container and recreate them using your Docker Hub repository.

#docker #node

What is GEEK

Buddha Community

Build and Run a Node.js App with Docker

NBB: Ad-hoc CLJS Scripting on Node.js

Nbb

Not babashka. Node.js babashka!?

Ad-hoc CLJS scripting on Node.js.

Status

Experimental. Please report issues here.

Goals and features

Nbb's main goal is to make it easy to get started with ad hoc CLJS scripting on Node.js.

Additional goals and features are:

  • Fast startup without relying on a custom version of Node.js.
  • Small artifact (current size is around 1.2MB).
  • First class macros.
  • Support building small TUI apps using Reagent.
  • Complement babashka with libraries from the Node.js ecosystem.

Requirements

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

#node #javascript

Aria Barnes

Aria Barnes

1622719015

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

#node.js development company in india #node js development company #hire node js developers #hire node.js developers in india #node.js development services #node.js development

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

If you look at the backend technology used by today’s most popular apps there is one thing you would find common among them and that is the use of NodeJS Framework. Yes, the NodeJS framework is that effective and successful.

If you wish to have a strong backend for efficient app performance then have NodeJS at the backend.

WebClues Infotech offers different levels of experienced and expert professionals for your app development needs. So hire a dedicated NodeJS developer from WebClues Infotech with your experience requirement and expertise.

So what are you waiting for? Get your app developed with strong performance parameters from WebClues Infotech

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Node JS Development Advantages - How Your App Will Benefit From This JavaScript Framework

Web development has been controlling the JavaScript system features for many years. Many big online sites use Java Script for their everyday operations. And recently there has been a change and a shift towards cross-platform mobile application development. The main software frameworks in work these days are React native, apache Cordova, native script and hybrid tools. In the last ten years, Node.JS has been used as a backend development framework. Developers nowadays want to learn and use the same technologies for one entire website. They do not want to learn an entire language for server development. And Node.JS is able to adapt all the functions and syntaxes to the backend services from JavaScript. If you do not know the languages or syntaxes for Node JS development, you can look for an online guide. These guides have a detailed overview of the additional functions and basic systems. You will also find simple tasks in these guides. To read more click on the link.

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sophia tondon

sophia tondon

1625114985

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.

Are you striving to develop an application using Node.js? But can’t decide which company to hire for NodeJS app development? Well! Don’t stress over it, as the following list of NodeJS app development companies is going to help you find the best partner.

Let’s take a glance at top NodeJS application development companies to hire developers in 2021 for developing a mind-blowing application solution.

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:

  • Review and rating
  • Enlisted by software peer & forums
  • Hourly price
  • Offered services
  • Year of experience (Average 8+ years)
  • Credibility & Excellence
  • Served clients and more

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.

#1. JSGuru

JSGuru is a top-rated NodeJS app development company with an innovative team of dedicated NodeJS developers engaged in catering best-class UI/UX design, software products, and AWS professional services.

It is a team of one of the most talented developers to hire for all types of innovative solution development, including social media, dating, enterprise, and business-oriented solutions. The company has worked for years with a number of startups and launched a variety of products by collaborating with big-name corporations like T-systems.

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.

  • Ratings: 4.9/5.0

  • Founded: 2006

  • Headquarters: Banja Luka, Bosnia, and Herzegovina

  • Price: Starting from $50/hour

Visit Website - https://www.valuecoders.com/blog/technology-and-apps/top-node-js-app-development-companies

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