express: initial commit

Author: gireeshpunathil

servers/express/basics/README.md

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+# Node.js Examples: express
+
+This directory contains some non-trivial examples for express. Express is an exemplary web server framework that implements a simple and powerful backend API interface. According to [their own website](https://expressjs.com/), express is a fast, unopinionated, minimalist web framework for Node.js.
+
+## References:
+- npm: https://www.npmjs.com/package/express
+- GitHub: https://github.com/expressjs/express
+- website: https://expressjs.com/
+
+
+## Usage:
+
+`npm install` to install as a local project
+`node index.js` to run as a standalone server
+`npm test` to run the tests
+
+## Contributors ✨
+
+Gireesh Punathil <gpunathi@in.ibm.com>
+
+This project follows the [all-contributors](https://github.com/all-contributors/all-contributors) specification. Contributions of any kind welcome!
+
+Contribution opportunities:
+ - adding a couple of more common scenarios
+ - tightening and widening the tests

servers/express/basics/app.js

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+// An express example project to showcase few abstractions
+// General layout is:
+//   - source-in the modules that implement individual functions
+//   - create an express server app
+//   - initialize each modules and setup their routes
+//   - listen for clients
+
+// main express module
+var express = require('express')
+
+// implements response redirect
+const redirect = require('./redirect.js')
+
+// implements session feature
+const session = require('./session.js')
+
+// implements a file upload function
+const upload = require('./upload.js')
+
+// a simple time retrieve function
+const time = require('./time.js')
+
+// a simple db operation
+const db = require('./db.js')
+
+// a default page that lists valid routes
+const defaults = require('./defaults.js')
+
+// create the express app
+var app = express()
+
+var server
+
+function start() {
+  // initialize the modules
+  redirect.setup(app)
+  session.setup(app)
+  upload.setup(app, express)
+  time.setup(app)
+  db.setup(app)
+  defaults.setup(app)
+
+  // listen for clients!
+  server = app.listen(12000, () => {
+    console.log('waiting for client connections!')
+    console.log('access \'http://localhost:12000\' to get started!')
+  })
+}
+
+function stop() {
+  db.dbstop()
+  server.close()
+}
+
+exports.stop = stop
+exports.start = start

servers/express/basics/db.js

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+// An example that shows a database operation.
+// I used an in-memory mongodb server for this
+// extract the client address, compute the current
+// time and store these in the db. Respond back
+// with the history of all client accesses.
+
+// server
+
+// source-in an in-memory server module
+const { MongoMemoryServer } = require('mongodb-memory-server')
+
+// server host
+const HOST = 'localhost'
+
+// server port
+const PORT = 13000
+
+// db instance name
+const DBNAME = 'mydb'
+
+// server instance, created through dbstart
+let mongod = null
+
+// start a server instance
+async function dbstart() {
+  mongod = new MongoMemoryServer({instance: {port: PORT, dbName: DBNAME}})
+  await mongod.getDbName()
+}
+
+// stop the server instance
+exports.dbstop = async function() {
+  if(mongod)
+    await mongod.stop()
+}
+
+// client
+
+async function exec(req, res) {
+  // source-in the db client
+  const MongoClient = require('mongodb').MongoClient
+
+  // start the db server
+  await dbstart()
+  const url = `mongodb://${HOST}:${PORT}`
+
+  // connect to the db server
+  MongoClient.connect(url, (err, client) => {
+    const db = client.db(DBNAME)
+    const collection = db.collection('documents')
+
+    // create a new record
+    var record = {}
+    record.time= new Date().toString()
+    record.client = req.connection.remoteAddress
+
+    // insert the record into the db
+    collection.insertMany([record], function(err, result) {
+
+      // retrieve all the records back
+      collection.find({}).toArray(function(err, docs) {
+
+        // send it as the response.
+        res.end(JSON.stringify(docs))
+        client.close()
+      })
+    })
+  })
+}
+
+exports.setup = function(app) {
+  app.get('/db', (req, res) => {
+    exec(req, res)
+  })
+}
+

servers/express/basics/defaults.js

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+exports.setup = function(app) {
+  app.get('/', (req, res) => {
+  res.write('welcome to express examples! the options are:\n\n')
+  res.write('/time : yields the current server time\n')
+  res.write('/session : tracks the client visit count, with an expiry\n')
+  res.write('/upload : a single file upload function\n')
+  res.write('/db : a simple db example, with an in-memory mongodb\n')
+  res.end('/redirect : forwards to /landing, a simple demonstration of redirect function\n')
+  })
+}

servers/express/basics/index.js

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+// Entry point of the app when you ran as a server
+
+var app = require('./app.js')
+app.start()

servers/express/basics/package.json

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+{
+  "name": "express-basics",
+  "version": "1.0.0",
+  "description": "Express basic function examples",
+  "main": "index.js",
+  "directories": {
+    "test": "test"
+  },
+  "scripts": {
+    "test": "tap test/*.js"
+  },
+  "keywords": [
+    "express",
+    "examples",
+    "nodejs"
+  ],
+  "author": "gpunathi@in.ibm.com",
+  "license": "Apache-2.0",
+  "devDependences": {
+    "tap": "^14.10.7"
+  },
+  "dependencies": {
+    "express": "^4.17.1",
+    "express-session": "^1.17.1",
+    "mongodb-memory-server": "^6.6.1",
+    "multer": "^1.4.2"
+  }
+}

servers/express/basics/public/index.html

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+<html>
+<body>
+<form action="/upload" method="post" enctype="multipart/form-data">
+Select file to upload:
+  <input type="file" name="upload" id="upload">
+  <input type="submit" value="upload file" name="submit">
+</form>
+</body>
+</html>
+

servers/express/basics/redirect.js

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+// An example that demonstrates
+// response redirect functionality
+// It redirects requests to /redirect, to /landing
+
+exports.setup = function(app) {
+  app.get('/redirect', (req, res) => {
+    res.redirect('/landing')
+  })
+
+  app.get('/landing', (req, res) => {
+    res.end('I am a redirect of /redirect')
+  })
+}
+

servers/express/basics/session.js

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+// An example that demonstrates
+// express session functionality
+// A session is created with expiry of 10 seconds
+// and attached with the express app
+
+var session = require('express-session')
+
+exports.setup = function(app) {
+  app.use(session({ secret: 'random secret', cookie: { maxAge: 10000}}))
+
+  app.get('/session', (req, res) => {
+    if (!req.session.views) {
+      req.session.views = 1
+    } else {
+      req.session.views++
+    }
+    if (req.session.views === 1)
+      res.end(`thanks for visiting ${req.session.views}st time! (session expires in 10 seconds)`)
+    else
+      res.end(`thanks for visiting ${req.session.views}th time! (session expires in 10 seconds)`)
+  })
+}

servers/express/basics/test/db.js

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+const request = require('request')
+const server = require('../app.js')
+const tap = require('tap')
+
+// start the server
+server.start()
+
+// test the /db route
+const url = 'http://localhost:12000/db'
+request(url, (err, res, body) => {
+  if(err)
+    tap.fail(err)
+  else
+    tap.match(body, /client/, 'db record has keyword "client" in it')
+  server.stop()
+})
+