Tag Archives: express.js

Tutorial: Node.js and MongoDB JSON REST API server with Mongoskin and Express.js

Update3: Expess 4 version of this tutorial is available at Express.js 4, Node.js and MongoDB REST API Tutorial, and github.com/azat-co/rest-api-express (master branch). This tutorial will work with Express 3.x.

Update2: “Mongoskin removed ‘db.collection.id’ and added some actionById methods” from this pull request with this code changes. To use the code in this post, just install an older version of Mongoskin (0.5.0?). The code in the GitHub will work with Mongoskin 1.3.20.

Update2: “Mongoskin removed ‘db.collection.id’ and added some actionById methods” from this pull request with this code changes. To use the code in this post, just install an older version of Mongoskin (0.5.0?)

Update: use the enhanced code from this repository github.com/azat-co/rest-api-express (express3 branch).

Note: This text is a part of Express.js Guide: The Comprehensive Book on Express.js.

This tutorial will walk you through writing test using the Mocha and Super Agent libraries and then use them in a test-driven development manner to build a Node.js free JSON REST API server utilizing Express.js framework and Mongoskin library for MongoDB. In this REST API server, we’ll perform create, read, update and delete (CRUD) operations and harness Express.js middleware concept with app.param() and app.use() methods.

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Express.js Tutorial: Instagram Gallery Example App with Storify API

Note: This text is a part of Express.js Guide: The Comprehensive Book on Express.js.

An example of an Express.js app using Storify API as a data source is a continuation of introduction to Express.js tutorials.

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Node.js MVC: Express.js + Derby.js Hello World Tutorial

DerbyJS — Node.js MVC Framework

Express.js is a popular node frameworks which uses middleware concept to enhance functionality of applications. Derby is a new sophisticated Model View Controller (MVC) framework which is designed to be used with Express as it’s middleware. Derby also comes with the support of Racer, data synchronization engine, and Handlebars-like template engine among many other features.

Derby.js Installation

Let’s set up a basic Derby application architecture without the use of scaffolding. Usually project generators are confusing when people just start to learn a new comprehensive framework. This is a bare minimum “Hello World” application tutorial that still illustrates Derby skeleton and demonstrates live-templates with websockets.

Of course we’ll need Node.js and NPM which can be obtained at nodejs.org. To install derby globally run:

$ npm install -g derby

To check the installation:

$ derby -V

My version as of April 2013 is 0.3.15. We should be good to go to creating our first app!

File Structure in a Derby.js App

This is the project folder structure:

project/
  -package.json
  -index.js
  -derby-app.js
  views/
    derby-app.html
  styles/
    derby-app.less

Dependencies for The Derby.js Project

Let’s include dependencies and other basic information in package.json file:

 {
  "name": "DerbyTutorial",
  "description": "",
  "version": "0.0.0",
  "main": "./server.js",
  "dependencies": {
    "derby": "*",
    "express": "3.x"
  },
  "private": true
}

Now we can run npm install which will download our dependencies into node_modules folder.

Views in Derby.js

Views must be in views folder and they must be either in index.html under a folder which has the same name as your derby app JavaScript file, i.e., views/derby-app/index.html, or be inside of a file which has the same name as your derby app JS file, i.e., derby-app.html.

In this example “Hello World” app we’ll use <Body:> template and {message} variable. Derby uses mustach-handlebars-like syntax for reactive binding. index.html looks like this:

<Body:>
  <input value="{message}"><h1>{message}</h1>

Same thing with Stylus/LESS files, in our example index.css has just one line:

h1 {
  color: blue;
}

To find out more about those wonderful CSS preprocessors check out documentation at Stylus and LESS.

Building The Main Derby.js Server

index.js is our main server file, and we begin it with an inclusion of dependencies with require() function:

var http = require('http'),
  express = require('express'),
  derby = require('derby'),
  derbyApp = require('./derby-app');

Last line is our derby application file derby-app.js.

Now we’re creating Express.js application (v3.x has significant differences between 2.x) and an HTTP server:

var expressApp = new express(),
  server = http.createServer(expressApp);

Derby uses Racer data synchronization library which we create like this:

var store = derby.createStore({
  listen: server
});

To fetch some data from back-end to the front-end we instantiate model object:

var model = store.createModel();

Most importantly we need to pass model and routes as middlewares to Express.js app. We need to expose public folder for socket.io to work properly.

expressApp.
  use(store.modelMiddleware()).
  use(express.static(__dirname + '/public')).
  use(derbyApp.router()).
  use(expressApp.router);

Now we can start the server on port 3001 (or any other):

server.listen(3001, function(){
  model.set('message', 'Hello World!');
});

Full code of index.js file:

var http = require('http'),
  express = require('express'),
  derby = require('derby'),
  derbyApp = require('./derby-app');

var expressApp = new express(),
  server = http.createServer(expressApp);

var store = derby.createStore({
  listen: server
});

var model = store.createModel();

expressApp.
  use(store.modelMiddleware()).
  use(express.static(__dirname + '/public')).
  use(derbyApp.router()).
  use(expressApp.router);

server.listen(3001, function(){
  model.set('message', 'Hello World!');
});

Derby.js Application

Finally, Derby app file which contains code for both a front-end and a back-end. Front-end only code is inside of app.ready() callback. To start, let’s require and create an app. Derby uses unusual construction (not the same familiar good old module.exports = app):

var derby = require('derby'),
  app = derby.createApp(module);

To make socket.io magic work we need to subscribe model attribute to its visual representation, in other words bind data and view. We can do it in the root route, and this is how we define it (patter is /, a.k.a. root):

app.get('/', function(page, model, params) {
  model.subscribe('message', function() {
    page.render();  
  })  
});

Full code of derby-app.js file:

var derby = require('derby'),
  app = derby.createApp(module);

app.get('/', function(page, model, params) {
  model.subscribe('message', function() {
    page.render();  
  })  
});  

Launching Hello World App

Now everything should be ready to boot our server. Execute node . or node index.js and open a browser at http://localhost:3001. You should be able to see something like this: http://cl.ly/image/3J1O0I3n1T46.

Derby + Express.js Hello World App

Passing Values to Back-End in Derby.js

Of course static data is not much, so we can slightly modify our app to make back-end and front-end pieces talks with each other.

In the server file index.js add store.afterDb to listen to set events on message attribute:

server.listen(3001, function(){
  model.set('message', 'Hello World!');
  store.afterDb('set','message', function(txn, doc, prevDoc, done){
    console.log(txn)
    done();
  }) 
});

Full code of index.js after modifications:

var http = require('http'),
  express = require('express'),
  derby = require('derby'),
  derbyApp = require('./derby-app');

var expressApp = new express(),
  server = http.createServer(expressApp);

var store = derby.createStore({
  listen: server
});

var model = store.createModel();

expressApp.
  use(store.modelMiddleware()).
  use(express.static(__dirname + '/public')).
  use(derbyApp.router()).
  use(expressApp.router);

server.listen(3001, function(){
  model.set('message', 'Hello World!');
  store.afterDb('set','message', function(txn, doc, prevDoc, done){
    console.log(txn)
    done();
  })   
});

In Derby application file derby-app.js add model.on() to app.ready():

  app.ready(function(model){
	    model.on('set', 'message',function(path, object){
	    console.log('message has been changed: '+ object);
	  })
  });

Full derby-app.js file after modifications:

var derby = require('derby'),
  app = derby.createApp(module);

app.get('/', function(page, model, params) {
  model.subscribe('message', function() {
    page.render();
  })
});

app.ready(function(model) {
  model.on('set', 'message', function(path, object) {
    console.log('message has been changed: ' + object);
  })
});

Now we’ll see logs both in the terminal window and in the browser Developer Tools console. The end result should look like this in the browser: http://cl.ly/image/0p3z1G3M1E2c, and like this in the terminal: http://cl.ly/image/322I1u002n38.

Hello World App: Browser Console Logs

Hello World App: Terminal Console Logs

For more magic in the persistence area, check out Racer’s db property. With it you can set up an automatic synch between views and database!

Let me know if you’re interested in any specific topic for future blog post and don’t forget to checkout my JavaScript books:

The full code of all the files in this Express.js + Derby Hello World app is available as a gist at https://gist.github.com/azat-co/5530311.

Intro to Express.js: Simple REST API app with Monk and MongoDB

Why?

After looking at Google Analytics stats I’ve realized that there is a demand for short Node.js tutorial and quick start guides. This is an introduction to probably the most popular (as of April 2013) Node.js framework Express.js.

Express.js — Node.js framework

Express.js — Node.js framework

mongoui

This app is a start of mongoui project. A phpMyAdmin counterpart for MongoDB written in Node.js. The goal is to provide a module with a nice web admin user interface. It will be something like Parse.com, Firebase.com, MongoHQ or MongoLab has but without trying it to any particular service. Why do we have to type db.users.findOne({'_id':ObjectId('...')}) any time we want to look up the user information? The alternative of MongoHub mac app is nice (and free) but clunky to use and not web based.

REST API app with Express.js and Monk

Ruby enthusiasts like to compare Express to Sinatra framework. It’s similarly flexible in the way how developers can build there apps. Application routes are set up in a similar manner, i.e., app.get('/products/:id', showProduct);. Currently Express.js is at version number 3.1. In addition to Express we’ll use Monk module.

We’ll use Node Package Manager which is usually come with a Node.js installation. If you don’t have it already you can get it at npmjs.org.

Create a new folder and NPM configuration file, package.json, in it with the following content:

{
  "name": "mongoui",
  "version": "0.0.1",
  "engines": {
    "node": ">= v0.6"
  },
  "dependencies": {
    "mongodb":"1.2.14",
    "monk": "0.7.1",
    "express": "3.1.0"
  }
}

Now run npm install to download and install modules into node_module folder. If everything went okay you’ll see bunch of folders in node_modules folders. All the code for our application will be in one file, index.js, to keep it simple stupid:

var mongo = require('mongodb');
var express = require('express');
var monk = require('monk');
var db =  monk('localhost:27017/test');
var app = new express();

app.use(express.static(__dirname + '/public'));
app.get('/',function(req,res){
  db.driver.admin.listDatabases(function(e,dbs){
      res.json(dbs);
  });
});
app.get('/collections',function(req,res){
  db.driver.collectionNames(function(e,names){
    res.json(names);
  })
});
app.get('/collections/:name',function(req,res){
  var collection = db.get(req.params.name);
  collection.find({},{limit:20},function(e,docs){
    res.json(docs);
  })
});
app.listen(3000)

Let break down the code piece by piece. Module declaration:

var mongo = require('mongodb');
var express = require('express');
var monk = require('monk');

Database and Express application instantiation:

var db =  monk('localhost:27017/test');
var app = new express();

Tell Express application to load and server static files (if there any) from public folder:

app.use(express.static(__dirname + '/public'));

Home page, a.k.a. root route, set up:

app.get('/',function(req,res){
  db.driver.admin.listDatabases(function(e,dbs){
      res.json(dbs);
  });
});

get() function just takes two parameters: string and function. The string can have slashes and colons, for example product/:id. The function must have two parapemets request and response. Request has all the information like query string parameters, session, headers and response is an object to with we output the results. In this case we do it by calling res.json() function. db.driver.admin.listDatabases() as you might guess give us a list of databases in async manner.

Two other routes are set up in a similar manner with get() function:

app.get('/collections',function(req,res){
  db.driver.collectionNames(function(e,names){
    res.json(names);
  })
});
app.get('/collections/:name',function(req,res){
  var collection = db.get(req.params.name);
  collection.find({},{limit:20},function(e,docs){
    res.json(docs);
  })
});

Express conveniently supports other HTTP verbs like post and update. In the case of setting up a post route we write this:

app.post('product/:id',function(req,res) {...});

Express also has support for middeware. Middleware is just a request function handler with three parameters: request, response, and next. For example:

app.post('product/:id', authenticateUser, validateProduct, addProduct);

function authenticateUser(req,res, next) {
  //check req.session for authentication
  next();
}

function validateProduct (req, res, next) {
   //validate submitted data
   next();
}

function addProduct (req, res) {
  //save data to database
}

validateProduct and authenticateProduct are middleware. They are usually put into separate file (or files) in a big projects.

Another way to set up middle ware in Express application is to use use() function. For example earlier we did this for static assets:

app.use(express.static(__dirname + '/public'));

We can also do it for error handlers:

app.use(errorHandler);

Assuming you have mongoDB installed this app will connect to it (localhost:27017) and display collection name and items in collections. To start mongo server:

$ mongod

to run app (keep the mongod terminal window open):

$ node .

or

$ node index.js

To see the app working, open http://localhost:3000 in Chrome with JSONViewer extension (to render JSON nicely).

Tom Hanks' The Polar Express

Tom Hanks’ The Polar Express