When building APIs, the need to upload files is expected, which can be images, text documents, scripts, pdfs, among others. In the development of this functionality, some problems can be found, such as the number of files, valid file types, sizes of these files, and several others. And to save us from these problems we have the Multer library. Multer is a node.js middleware for handling multipart/form-data that is used to send files in forms.
The first step is to create a NodeJS project on your computer.
\nIn your terminal, type the following command:
\nyarn add express* You can also use NPM for installation
\nCreate a file named app.js inside the src/ folder. The next step is to start our Express server in our app.js
const express = require("express")\nconst app = express()\n\napp.listen(3000 || process.env.PORT, () => {\n console.log("Server on...")\n})With the project created, configured and with Express installed, we will add the multer to our project.
\nyarn add multerThe next step is to import the multer into our app.js file.
const multer = require("multer")We are almost there. Now create a folder called uploads where we will store the uploaded files.
Now we are at a very important stage which is the configuration of diskStorage. DiskStorage is a method made available by multer where we configure the destination of the file, the name of the file and we can also add validations regarding the type of the file. These settings are according to the needs of your project. Below I will leave an elementary example of the configuration.
const storage = multer.diskStorage({\n destination: (req, file, cb) => {\n cb(null, "uploads/")\n },\n filename: (req, file, cb) => {\n cb(null, Date.now() + "-" + file.originalname)\n },\n})In the configuration above, we mentioned the destination for the uploaded files and also change the name of the file .
\nconst uploadStorage = multer({ storage: storage })\n\n// Single file\napp.post("/upload/single", uploadStorage.single("file"), (req, res) => {\n console.log(req.file)\n return res.send("Single file")\n})\n\n//Multiple files\napp.post("/upload/multiple", uploadStorage.array("file", 10), (req, res) => {\n console.log(req.files)\n return res.send("Multiple files")\n})In the code snippet above, we created 2 POST routes for sending files. The first /upload/single route receives only a single file, note that the uploadStorage variable receives our diskStorage settings. As a middleware in the route, it calls the single method for uploading a single file. The /upload/multiple route receives several files, but with a maximum limit of 10 files, note that the uploadStorage variable now calls the ʻarray` method for uploading multiple files.
With all the settings done, our little API is already able to store the files sent.
\nconst express = require("express")\nconst multer = require("multer")\n\nconst app = express()\n\nconst storage = multer.diskStorage({\n destination: (req, file, cb) => {\n cb(null, "uploads/")\n },\n filename: (req, file, cb) => {\n cb(null, Date.now() + "-" + file.originalname)\n },\n})\n\nconst uploadStorage = multer({ storage: storage })\n\n// Single file\napp.post("/upload/single", uploadStorage.single("file"), (req, res) => {\n console.log(req.file)\n return res.send("Single file")\n})\n//Multiple files\napp.post("/upload/multiple", uploadStorage.array("file", 10), (req, res) => {\n console.log(req.files)\n return res.send("Multiple files")\n})\n\napp.listen(3000 || process.env.PORT, () => {\n console.log("Server on...")\n})Now it's up to you!
\n","frontmatter":{"date":"October 12, 2020","updated_date":null,"title":"Upload files using NodeJS + Multer","tags":["NodeJs","Express","Multer"],"coverImage":{"childImageSharp":{"fluid":{"aspectRatio":1.5037593984962405,"src":"/static/49a3115a8c11e7fd9aca612e846c5936/ee604/node-multer-upload.png","srcSet":"/static/49a3115a8c11e7fd9aca612e846c5936/69585/node-multer-upload.png 200w,\n/static/49a3115a8c11e7fd9aca612e846c5936/497c6/node-multer-upload.png 400w,\n/static/49a3115a8c11e7fd9aca612e846c5936/ee604/node-multer-upload.png 800w,\n/static/49a3115a8c11e7fd9aca612e846c5936/f3583/node-multer-upload.png 1200w","sizes":"(max-width: 800px) 100vw, 800px"}}},"author":{"id":"Gabriel Rabelo","github":"gabrielrab","avatar":null}}}},{"node":{"fields":{"slug":"/engineering/creating-a-google-hangout-bot-with-express-and-node-js/"},"html":"Time Required: 20 minutes.
\nTechnologies: Express, Node.js, JavaScript.
\nPrerequisites:
This tutorial will go over how to build a bot that will respond to pings (i.e. @
Create a new project with the file ‘app.js’.
\nOpen command line/terminal, and navigate to your project directory. Run ‘npm init’, and press enter until package.json is created. Next, install the following dependencies:
npm install express --savenpm install body-parser --savenpm install googleapis --savenpm install unirest --saveIn ‘app.js’, let’s setup our server:
\nconst express = require('express');\nconst bodyParser = require('body-parser');\nconst { google } = require('googleapis');\n\nconst app = express();\n\napp.use(bodyParser.urlencoded({\n extended: false\n}));\n\napp.use(bodyParser.json());\n\napp.listen(8100, function() {\n console.log('App listening on port 8100.');\n});Running ‘node app.js’ will now create a local server on port 8100.
\nThe bot will respond to pings through a HTTP POST endpoint. Create one with express:
\napp.post('/', function(req, res) {\n console.log('someone pinged @');\n\n if (req.body.type === 'MESSAGE') {\n return res.json({\n text: 'sleeping...'\n });\n }\n});The bot will respond with the text: ‘sleeping…’.
\nSynchronously responding to messages simply requires us to return a response to Google. The downside to this is the 30 second time limit before Google no longer accepts responses to the request. For instance, this would be a problem if you were building some kind of reminder app; the bot wouldn't be able to synchronously respond after 30 seconds. This is where async responses come in.
\nTo show this, we will have our bot post to a chat room every 1 minute.
\nSending async messages to Google API requires a Service Account for authentication. Once authenticated, we can make a POST request to a Google API URL that will create a message.
\nSo first, create a Google Service Account following these steps. Take the downloaded JSON file and put it in the root directory of your project. Here, we renamed it to googlekeys.json:
\nconst gkeys = require('./googlekeys.json');We will be making POST requests using Unirest:
\nconst unirest = require('unirest');Now generate a JWT that will be used in our POST request:
\nfunction getJWT() {\n return new Promise(function(resolve, reject) {\n let jwtClient = new google.auth.JWT(\n gkeys.client_email,\n null,\n gkeys.private_key, ['https://www.googleapis.com/auth/chat.bot']\n );\n\n jwtClient.authorize(function(err, tokens) {\n if (err) {\n console.log('Error create JWT hangoutchat');\n reject(err);\n } else {\n resolve(tokens.access_token);\n }\n });\n });\n}Here is our function for posting messages. ROOM-ID can be found in the URL of the hangout chat room page i.e.: https://chat.google.com/u/0/room/{ROOM-ID}
function postMessage(count) {\n return new Promise(function(resolve, reject) {\n getJWT().then(function(token) {\n unirest.post('https://chat.googleapis.com/v1/spaces/' + {ROOM-ID} + '/messages')\n .headers({\n "Content-Type": "application/json",\n "Authorization": "Bearer " + token\n })\n .send(JSON.stringify({\n 'text': 'Hello! This is message number ' + count,\n }))\n .end(function(res) {\n resolve();\n });\n }).catch(function(err) {\n reject(err);\n });\n });\n}Finally, add the code that will repeat our post every minute.
\nconst timer = require('timers');\n\napp.listen(8100, function() {\n console.log('App listening on port 8100.');\n\n let count = 0;\n timer.setInterval(function() {\n postMessage(count += 1);\n }, 60000);\n});Expose your local server to public (we used ngrok).
\nLogin to developer console. Create a new project, and enable Hangout Chat API. Under configuration, set:
\nRestart your local server, and that’s it! Make sure you have your bot added to the chat room, and you can ping it by sending @
There are a lot of different ways to further extend this bot, such as setting reminders/notifications, making to-do lists, displaying server logs, and interacting with API’s.
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