Jack Downson

Jack Downson

1566623184

Create Restful CRUD API with Node.js MongoDB and Express.js

In simple terms, REST stands for Representational State Transfer. It is an architectural style design for distributed hypermedia, or an Application Programming Interface (API). In REST, we use various standard HTTP methods like GET, POST, PUT and DELETE to perform any CRUD operation on resource.

Resource

In REST, everything is Resource. A resource can be an image, document, a temporary service, a collection of other resource, and any other object. Each resource has resource identifier to identify it.

HTTP Methods for CRUD

As per REST guidelines, we should use only HTTP methods to perform CRUD operation on any resource. In this blog, we are going to use 4 HTTP methods like GET, POST, PUT and DELETE to make our REST API.

Let’s have a brief introduction of each http method here.

  • HTTP GET

The HTTP GET is used to Read or Retrieve any resource. It returns the XML or JSON data with HTTP status code of 200. GET method is considered as safe, because we are just getting or reading the resource data, not doing any changes in the resource data.

  • HTTP GET

The HTTP POST is used to Create a new resource. On successful creation of resource, it will return HTTP status code of 201, a Location header with a link to the newly created resource.

  • HTTP GET

The HTTP PUT is used to Update any existing resource. On successful, it will return HTTP status code of 200.

  • HTTP GET

The HTTP DELETE, as the name suggests, is used to Delete any existing resource. On successful, it will return HTTP status code of 200.

HTTP MethodsCRUDStatus CodeGETRead200 (OK), 404 (Not Found)POSTCreate201 (OK), 404 (Not Found), PUTUpdate200 (OK), 204 (No Content), 404 (Not Found)DELETEDelete200 (OK), 404 (Not Found)Let’s move forward into the details of other pieces of creating our REST API.

Express.js

We are going to use Express.js or simply Express. It is a web application framework for Node.js. It has been released as free and open source software. You can create web application and APIs using Express. It has support for routing, middleware, view system etc.

Mongoose

Mongoose is Object Document Mapping or ODM tool for Node.js and MongoDB. Mongoose provide a straight-forward, schema based solution to model to your application data. It includes built-in type casting, validation, query building, business logic hooks and many more.

Prerequisites

You must have Node.js and MongoDB installed on your machine. Click the below links, if you don’t have any one of them.

Install Node.js

Install MongoDB

For MongoDB, I am using mLab free account for online MongoDB database. You can try this one as well, instead of installing on your local machine.
Database-as-a-Service for MongoDB

Install Postman – Google Chrome for testing purpose.

After setting up prerequisites, let move forward to build our application.

Application Introduction

In our application, we are going to create a product based application. We will use REST APIs to create, update, get and delete the product. Let’s go to create our application.

1. Create package.json

Let’s create a folder, and start with creating package.json file first. Use this command in your terminal window.

For MongoDB, I am using mLab free account for online MongoDB database. You can try this one as well, instead of installing on your local machine.#### package.json

{
  "name": "product-app",
  "version": "1.0.0",
  "description": "This is zepbook product app",
  "main": "server.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "ZeptoBook",
  "license": "MIT"
}

If you notice line 5, we have defined server.js as our main entry point.

2. Install Packages

Let’s install all the express, mongoose and body-parser package dependencies in our app.

For MongoDB, I am using mLab free account for online MongoDB database. You can try this one as well, instead of installing on your local machine.
Once these packages installed successfully, our package.json file will be updated automatically. Our latest file will be like this.

package.json

{
  "name": "product-app",
  "version": "1.0.0",
  "description": "This is zepbook product app",
  "main": "server.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "ZeptoBook",
  "license": "MIT",
  "dependencies": {
    "body-parser": "^1.18.3",
    "express": "^4.16.4",
    "mongoose": "^5.4.2"
  }
}

Notice dependencies section of our file, all these packages are mentioned there.

3. Creating Our Server

Let’s create a server.js file in the root directory of the application.

server.js

// get dependencies
const express = require('express');
const bodyParser = require('body-parser');

const app = express();

// parse requests
app.use(bodyParser.urlencoded({ extended: false }))
app.use(bodyParser.json())

// default route
app.get('/', (req, res) => {
    res.json({"message": "Welcome to ZeptoBook Product app"});
});

// listen on port 3000
app.listen(3000, () => {
    console.log("Server is listening on port 3000");
});
view raw

Let’s briefly review our above code. First of all, we imported the required dependencies in our server.js file.

body-parser

It is Node.js body parser middleware. It parse the incoming request bodies in a middleware before your handlers, available under the req.body property.

Learn more about bodyParser.urlencoded([options])

Learn more about bodyParser.json([options])

Then, we define a default route using GET Http method. By default, it will return our message on default url.

Finally, we are going to listen all incoming requests on port 3000.

4. Run the server

Once everything is all set, let’s wake up our server by running this command in our terminal window.

For MongoDB, I am using mLab free account for online MongoDB database. You can try this one as well, instead of installing on your local machine.> For MongoDB, I am using mLab free account for online MongoDB database. You can try this one as well, instead of installing on your local machine.#### 5. Create Configuration file

Let’s create a config file in our app, where we can define various constants like dbconnection or port number instead of hard-coded it everywhere. So, create a config.js file in your app folder.

config.js

module.exports = {
    url: 'mongodb://<dbUserName>:<dbUserPassword>@ds251002.mlab.com:51002/adeshtestdb',
    serverport: 3000 
}

So, here I mentioned two constants in config.js file.

  • HTTP GET

6. Connecting to Database

Let’s connect with our MongoDb database. Add these lines of codes in server.js file after the app.use(bodyParser.json());

// Configuring the database
const config = require('./config.js');
const mongoose = require('mongoose');

mongoose.Promise = global.Promise;

// Connecting to the database
mongoose.connect(config.url, {
    useNewUrlParser: true
}).then(() => {
    console.log("Successfully connected to the database");    
}).catch(err => {
    console.log('Could not connect to the database. Exiting now...', err);
    process.exit();
});

Also, we are going to replace our hard-coded server port with our config constant in server.js file

// listen on port 3000
app.listen(config.serverport, () => {
    console.log("Server is listening on port 3000");
});

Here, you can see, we are now using config.serverport in app.listen().

Now, run again the server using this command.

For MongoDB, I am using mLab free account for online MongoDB database. You can try this one as well, instead of installing on your local machine.> For MongoDB, I am using mLab free account for online MongoDB database. You can try this one as well, instead of installing on your local machine.> For MongoDB, I am using mLab free account for online MongoDB database. You can try this one as well, instead of installing on your local machine.#### 7. Creating Product Model

Let’s create a product model in our app folder in order to save the data in our db. Create a product.model.js file in your app.

product.model.js

const mongoose = require('mongoose');

const ProductSchema = mongoose.Schema({
    title: String,
    description: String,
    price: Number,
    company: String
}, {
    timestamps: true
});

module.exports = mongoose.model('Products', ProductSchema);

Here, we have defined our ProductSchema with following properties. Along with this, we also set timestamps property to true. This property will add two fields automatically to schema. These fields are : createdAt and updatedAt in your schema.

8. Creating our Controller’s functions

We are going to write all functions related to create, retrieve, update and delete products in our controller file. Let’s create a controller file named product.controller.js in your app folder.

product.controller.js

const Product = require('./product.model.js');

//Create new Product
exports.create = (req, res) => {
    // Request validation
    if(!req.body) {
        return res.status(400).send({
            message: "Product content can not be empty"
        });
    }

    // Create a Product
    const product = new Product({
        title: req.body.title || "No product title", 
        description: req.body.description,
        price: req.body.price,
        company: req.body.company
    });

    // Save Product in the database
    product.save()
    .then(data => {
        res.send(data);
    }).catch(err => {
        res.status(500).send({
            message: err.message || "Something wrong while creating the product."
        });
    });
};

// Retrieve all products from the database.
exports.findAll = (req, res) => {
    Product.find()
    .then(products => {
        res.send(products);
    }).catch(err => {
        res.status(500).send({
            message: err.message || "Something wrong while retrieving products."
        });
    });
};

// Find a single product with a productId
exports.findOne = (req, res) => {
    Product.findById(req.params.productId)
    .then(product => {
        if(!product) {
            return res.status(404).send({
                message: "Product not found with id " + req.params.productId
            });            
        }
        res.send(product);
    }).catch(err => {
        if(err.kind === 'ObjectId') {
            return res.status(404).send({
                message: "Product not found with id " + req.params.productId
            });                
        }
        return res.status(500).send({
            message: "Something wrong retrieving product with id " + req.params.productId
        });
    });
};

// Update a product
exports.update = (req, res) => {
    // Validate Request
    if(!req.body) {
        return res.status(400).send({
            message: "Product content can not be empty"
        });
    }

    // Find and update product with the request body
    Product.findByIdAndUpdate(req.params.productId, {
        title: req.body.title || "No product title", 
        description: req.body.description,
        price: req.body.price,
        company: req.body.company
    }, {new: true})
    .then(product => {
        if(!product) {
            return res.status(404).send({
                message: "Product not found with id " + req.params.productId
            });
        }
        res.send(product);
    }).catch(err => {
        if(err.kind === 'ObjectId') {
            return res.status(404).send({
                message: "Product not found with id " + req.params.productId
            });                
        }
        return res.status(500).send({
            message: "Something wrong updating note with id " + req.params.productId
        });
    });
};

// Delete a note with the specified noteId in the request
exports.delete = (req, res) => {
    Product.findByIdAndRemove(req.params.productId)
    .then(product => {
        if(!product) {
            return res.status(404).send({
                message: "Product not found with id " + req.params.productId
            });
        }
        res.send({message: "Product deleted successfully!"});
    }).catch(err => {
        if(err.kind === 'ObjectId' || err.name === 'NotFound') {
            return res.status(404).send({
                message: "Product not found with id " + req.params.productId
            });                
        }
        return res.status(500).send({
            message: "Could not delete product with id " + req.params.productId
        });
    });
};

9. Defining Product API’s Routes

Next step is to create our api routes. Create a product.routes.js file in your app folder.

product.routes.js

module.exports = (app) => {
    const products = require('./product.controller.js');

    // Create a new Product
    app.post('/products', products.create);

    // Retrieve all Products
    app.get('/products', products.findAll);

    // Retrieve a single Product with productId
    app.get('/products/:productId', products.findOne);

    // Update a Note with productId
    app.put('/products/:productId', products.update);

    // Delete a Note with productId
    app.delete('/products/:productId', products.delete);
}

Note: import this route file in our server.js file after these lines. See line 4 in the below code.

// Configuring the database

const config = require('./config.js');
const mongoose = require('mongoose');
require('./product.routes.js')(app); //Add route file he

server.js

10. Enable the CORS

If you try to access your api routes through your client-side app, you might face Access-Control-Allow-Origin error messages. So, in order to avoid these message, we are also enabling CORS in our server.js file.

server.js

//Enable CORS for all HTTP methods

app.use(function(req, res, next) {
res.header("Access-Control-Allow-Origin", "*");
res.header("Access-Control-Allow-Methods", "GET, PUT, POST, DELETE, OPTIONS");
res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
next();
});

So, this will be our final server.js file.

server.js

// get dependencies
const express = require('express');
const bodyParser = require('body-parser');

const app = express();

// parse requests
app.use(bodyParser.urlencoded({ extended: true }));
app.use(bodyParser.json());

//Enable CORS for all HTTP methods
app.use(function(req, res, next) {
&nbsp;&nbsp;&nbsp; res.header("Access-Control-Allow-Origin", "*");
&nbsp;&nbsp;&nbsp; res.header("Access-Control-Allow-Methods", "GET, PUT, POST, DELETE, OPTIONS");
&nbsp;&nbsp;&nbsp; res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
&nbsp;&nbsp;&nbsp; next();
&nbsp; });

// Configuring the database
const config = require('./config.js');
const mongoose = require('mongoose');
require('./product.routes.js')(app);

mongoose.Promise = global.Promise;

// Connecting to the database
mongoose.connect(config.url, {
&nbsp;&nbsp;&nbsp; useNewUrlParser: true
}).then(() => {
&nbsp;&nbsp;&nbsp; console.log("Successfully connected to the database");&nbsp;&nbsp; &nbsp;
}).catch(err => {
&nbsp;&nbsp;&nbsp; console.log('Could not connect to the database. Exiting now...', err);
&nbsp;&nbsp;&nbsp; process.exit();
});

// default route
app.get('/', (req, res) => {
&nbsp;&nbsp;&nbsp; res.json({"message": "Welcome to ZeptoBook Product app"});
});

// listen on port 3000
app.listen(config.serverport, () => {
&nbsp;&nbsp;&nbsp; console.log("Server is listening on port 3000");
});

This will be our project structure.

Testing our REST APIs

Now, it’s time to test our all REST APIs for CRUD Operation.

  • HTTP GET

I have added few products in the database. See the below screen shot.

  • HTTP GET

  • HTTP GET

  • HTTP GET

Before Update

After Update

  • HTTP GET

Download

You can download all the project files from GitHub.

Download Project Files

Further reading:

Build a REST API to manage users and roles using Firebase and Node.js

Using Node 11.7 Worker Threads With RxJS Observable

How to build a command-line chat app using SocketIO

Running a Node REPL Within Your App’s Environment

Use MongoDB Node.js Native Driver Without Mongoose

Deploying a Node 12 Function to Cloud Run

Video Streaming with Node.js

#node-js #javascript

What is GEEK

Buddha Community

Create Restful CRUD API with Node.js MongoDB and Express.js
Easter  Deckow

Easter Deckow

1655630160

PyTumblr: A Python Tumblr API v2 Client

PyTumblr

Installation

Install via pip:

$ pip install pytumblr

Install from source:

$ git clone https://github.com/tumblr/pytumblr.git
$ cd pytumblr
$ python setup.py install

Usage

Create a client

A pytumblr.TumblrRestClient is the object you'll make all of your calls to the Tumblr API through. Creating one is this easy:

client = pytumblr.TumblrRestClient(
    '<consumer_key>',
    '<consumer_secret>',
    '<oauth_token>',
    '<oauth_secret>',
)

client.info() # Grabs the current user information

Two easy ways to get your credentials to are:

  1. The built-in interactive_console.py tool (if you already have a consumer key & secret)
  2. The Tumblr API console at https://api.tumblr.com/console
  3. Get sample login code at https://api.tumblr.com/console/calls/user/info

Supported Methods

User Methods

client.info() # get information about the authenticating user
client.dashboard() # get the dashboard for the authenticating user
client.likes() # get the likes for the authenticating user
client.following() # get the blogs followed by the authenticating user

client.follow('codingjester.tumblr.com') # follow a blog
client.unfollow('codingjester.tumblr.com') # unfollow a blog

client.like(id, reblogkey) # like a post
client.unlike(id, reblogkey) # unlike a post

Blog Methods

client.blog_info(blogName) # get information about a blog
client.posts(blogName, **params) # get posts for a blog
client.avatar(blogName) # get the avatar for a blog
client.blog_likes(blogName) # get the likes on a blog
client.followers(blogName) # get the followers of a blog
client.blog_following(blogName) # get the publicly exposed blogs that [blogName] follows
client.queue(blogName) # get the queue for a given blog
client.submission(blogName) # get the submissions for a given blog

Post Methods

Creating posts

PyTumblr lets you create all of the various types that Tumblr supports. When using these types there are a few defaults that are able to be used with any post type.

The default supported types are described below.

  • state - a string, the state of the post. Supported types are published, draft, queue, private
  • tags - a list, a list of strings that you want tagged on the post. eg: ["testing", "magic", "1"]
  • tweet - a string, the string of the customized tweet you want. eg: "Man I love my mega awesome post!"
  • date - a string, the customized GMT that you want
  • format - a string, the format that your post is in. Support types are html or markdown
  • slug - a string, the slug for the url of the post you want

We'll show examples throughout of these default examples while showcasing all the specific post types.

Creating a photo post

Creating a photo post supports a bunch of different options plus the described default options * caption - a string, the user supplied caption * link - a string, the "click-through" url for the photo * source - a string, the url for the photo you want to use (use this or the data parameter) * data - a list or string, a list of filepaths or a single file path for multipart file upload

#Creates a photo post using a source URL
client.create_photo(blogName, state="published", tags=["testing", "ok"],
                    source="https://68.media.tumblr.com/b965fbb2e501610a29d80ffb6fb3e1ad/tumblr_n55vdeTse11rn1906o1_500.jpg")

#Creates a photo post using a local filepath
client.create_photo(blogName, state="queue", tags=["testing", "ok"],
                    tweet="Woah this is an incredible sweet post [URL]",
                    data="/Users/johnb/path/to/my/image.jpg")

#Creates a photoset post using several local filepaths
client.create_photo(blogName, state="draft", tags=["jb is cool"], format="markdown",
                    data=["/Users/johnb/path/to/my/image.jpg", "/Users/johnb/Pictures/kittens.jpg"],
                    caption="## Mega sweet kittens")

Creating a text post

Creating a text post supports the same options as default and just a two other parameters * title - a string, the optional title for the post. Supports markdown or html * body - a string, the body of the of the post. Supports markdown or html

#Creating a text post
client.create_text(blogName, state="published", slug="testing-text-posts", title="Testing", body="testing1 2 3 4")

Creating a quote post

Creating a quote post supports the same options as default and two other parameter * quote - a string, the full text of the qote. Supports markdown or html * source - a string, the cited source. HTML supported

#Creating a quote post
client.create_quote(blogName, state="queue", quote="I am the Walrus", source="Ringo")

Creating a link post

  • title - a string, the title of post that you want. Supports HTML entities.
  • url - a string, the url that you want to create a link post for.
  • description - a string, the desciption of the link that you have
#Create a link post
client.create_link(blogName, title="I like to search things, you should too.", url="https://duckduckgo.com",
                   description="Search is pretty cool when a duck does it.")

Creating a chat post

Creating a chat post supports the same options as default and two other parameters * title - a string, the title of the chat post * conversation - a string, the text of the conversation/chat, with diablog labels (no html)

#Create a chat post
chat = """John: Testing can be fun!
Renee: Testing is tedious and so are you.
John: Aw.
"""
client.create_chat(blogName, title="Renee just doesn't understand.", conversation=chat, tags=["renee", "testing"])

Creating an audio post

Creating an audio post allows for all default options and a has 3 other parameters. The only thing to keep in mind while dealing with audio posts is to make sure that you use the external_url parameter or data. You cannot use both at the same time. * caption - a string, the caption for your post * external_url - a string, the url of the site that hosts the audio file * data - a string, the filepath of the audio file you want to upload to Tumblr

#Creating an audio file
client.create_audio(blogName, caption="Rock out.", data="/Users/johnb/Music/my/new/sweet/album.mp3")

#lets use soundcloud!
client.create_audio(blogName, caption="Mega rock out.", external_url="https://soundcloud.com/skrillex/sets/recess")

Creating a video post

Creating a video post allows for all default options and has three other options. Like the other post types, it has some restrictions. You cannot use the embed and data parameters at the same time. * caption - a string, the caption for your post * embed - a string, the HTML embed code for the video * data - a string, the path of the file you want to upload

#Creating an upload from YouTube
client.create_video(blogName, caption="Jon Snow. Mega ridiculous sword.",
                    embed="http://www.youtube.com/watch?v=40pUYLacrj4")

#Creating a video post from local file
client.create_video(blogName, caption="testing", data="/Users/johnb/testing/ok/blah.mov")

Editing a post

Updating a post requires you knowing what type a post you're updating. You'll be able to supply to the post any of the options given above for updates.

client.edit_post(blogName, id=post_id, type="text", title="Updated")
client.edit_post(blogName, id=post_id, type="photo", data="/Users/johnb/mega/awesome.jpg")

Reblogging a Post

Reblogging a post just requires knowing the post id and the reblog key, which is supplied in the JSON of any post object.

client.reblog(blogName, id=125356, reblog_key="reblog_key")

Deleting a post

Deleting just requires that you own the post and have the post id

client.delete_post(blogName, 123456) # Deletes your post :(

A note on tags: When passing tags, as params, please pass them as a list (not a comma-separated string):

client.create_text(blogName, tags=['hello', 'world'], ...)

Getting notes for a post

In order to get the notes for a post, you need to have the post id and the blog that it is on.

data = client.notes(blogName, id='123456')

The results include a timestamp you can use to make future calls.

data = client.notes(blogName, id='123456', before_timestamp=data["_links"]["next"]["query_params"]["before_timestamp"])

Tagged Methods

# get posts with a given tag
client.tagged(tag, **params)

Using the interactive console

This client comes with a nice interactive console to run you through the OAuth process, grab your tokens (and store them for future use).

You'll need pyyaml installed to run it, but then it's just:

$ python interactive-console.py

and away you go! Tokens are stored in ~/.tumblr and are also shared by other Tumblr API clients like the Ruby client.

Running tests

The tests (and coverage reports) are run with nose, like this:

python setup.py test

Author: tumblr
Source Code: https://github.com/tumblr/pytumblr
License: Apache-2.0 license

#python #api 

Wilford  Pagac

Wilford Pagac

1594289280

What is REST API? An Overview | Liquid Web

What is REST?

The REST acronym is defined as a “REpresentational State Transfer” and is designed to take advantage of existing HTTP protocols when used for Web APIs. It is very flexible in that it is not tied to resources or methods and has the ability to handle different calls and data formats. Because REST API is not constrained to an XML format like SOAP, it can return multiple other formats depending on what is needed. If a service adheres to this style, it is considered a “RESTful” application. REST allows components to access and manage functions within another application.

REST was initially defined in a dissertation by Roy Fielding’s twenty years ago. He proposed these standards as an alternative to SOAP (The Simple Object Access Protocol is a simple standard for accessing objects and exchanging structured messages within a distributed computing environment). REST (or RESTful) defines the general rules used to regulate the interactions between web apps utilizing the HTTP protocol for CRUD (create, retrieve, update, delete) operations.

What is an API?

An API (or Application Programming Interface) provides a method of interaction between two systems.

What is a RESTful API?

A RESTful API (or application program interface) uses HTTP requests to GET, PUT, POST, and DELETE data following the REST standards. This allows two pieces of software to communicate with each other. In essence, REST API is a set of remote calls using standard methods to return data in a specific format.

The systems that interact in this manner can be very different. Each app may use a unique programming language, operating system, database, etc. So, how do we create a system that can easily communicate and understand other apps?? This is where the Rest API is used as an interaction system.

When using a RESTful API, we should determine in advance what resources we want to expose to the outside world. Typically, the RESTful API service is implemented, keeping the following ideas in mind:

  • Format: There should be no restrictions on the data exchange format
  • Implementation: REST is based entirely on HTTP
  • Service Definition: Because REST is very flexible, API can be modified to ensure the application understands the request/response format.
  • The RESTful API focuses on resources and how efficiently you perform operations with it using HTTP.

The features of the REST API design style state:

  • Each entity must have a unique identifier.
  • Standard methods should be used to read and modify data.
  • It should provide support for different types of resources.
  • The interactions should be stateless.

For REST to fit this model, we must adhere to the following rules:

  • Client-Server Architecture: The interface is separate from the server-side data repository. This affords flexibility and the development of components independently of each other.
  • Detachment: The client connections are not stored on the server between requests.
  • Cacheability: It must be explicitly stated whether the client can store responses.
  • Multi-level: The API should work whether it interacts directly with a server or through an additional layer, like a load balancer.

#tutorials #api #application #application programming interface #crud #http #json #programming #protocols #representational state transfer #rest #rest api #rest api graphql #rest api json #rest api xml #restful #soap #xml #yaml

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

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