Node.js - Auto Refresh In Dev

Question

I am trying to improve the DEV experience in my Node. To do that, I want to:

a) restart my server when server-side code is changed
b) refresh the browser when client-side code is changes.

In an effort to accomplish this, I began integrating nodemon and browserSync into my gulp script.

In my gulp script, I have the following task:

gulp.task('startDevEnv', function(done) {
    // Begin watching for server-side file changes
    nodemon(
        { script: input.server, ignore:[input.views] })
        .on('start', function () {
            browserSync.init({
                proxy: "http://localhost:3002"
            });
        })
    ;    

    // Begin watching client-side file changes
    gulp.watch([ input.css, input.js, input.html ], function() { browserSync.reload(); });
    done();
});

When the above task runs, my browser opens to http://localhost:3000/. My app is visible as expected. However, in the console window, I notice:

Error: listen EADDRINUSE :::3002

I understand to some extend. I have app.set('port', process.env.PORT || 3002); in my server.js file. Yet, I thought that was purpose of setting the proxy value. Still, whenever I make a code change, I see the following related error in my console window:

[07:08:19] [nodemon] restarting due to changes...
[07:08:19] [nodemon] starting `node ./dist/server.js`
events.js:142
      throw er; // Unhandled 'error' event
      ^

TypeError: args.cb is not a function
    at Object.init (/Users/me/Website/Develop/node_modules/browser-sync/lib/public/init.js:25:25)
    at null.<anonymous> (/Users/me/Website/Develop/gulpfile.js:142:25)
    at emitNone (events.js:73:20)
    at emit (events.js:167:7)
    at Object.run (/Users/me/Website/Develop/node_modules/nodemon/lib/monitor/run.js:97:7)
    at Function.run.kill (/Users/me/Website/Develop/node_modules/nodemon/lib/monitor/run.js:221:7)
    at null.<anonymous> (/Users/me/Website/Develop/node_modules/nodemon/lib/monitor/run.js:333:7)
    at emitOne (events.js:83:20)
    at emit (events.js:170:7)
    at restartBus (/Users/me/Website/Develop/node_modules/nodemon/lib/monitor/watch.js:162:7)
Me-MBP:Develop me$ events.js:142
      throw er; // Unhandled 'error' event
      ^

Error: listen EADDRINUSE :::3002
    at Object.exports._errnoException (util.js:856:11)
    at exports._exceptionWithHostPort (util.js:879:20)
    at Server._listen2 (net.js:1238:14)
    at listen (net.js:1274:10)
    at Server.listen (net.js:1370:5)
    at Object.<anonymous> (/Users/me/Website/Develop/dist/server.js:70:8)
    at Module._compile (module.js:399:26)
    at Object.Module._extensions..js (module.js:406:10)
    at Module.load (module.js:345:32)
    at Function.Module._load (module.js:302:12)

At this point, my code changes do not appear in my browser. I do not understand what I'm doing wrong. I suspect I have my ports misconfigured. But, I'm not really sure how they should be setup.

By default BrowserSync uses port 3000. BrowserSync also uses port 3001 for the BrowserSync UI. For these two reasons, I thought I would set the port to 3002 in my server.js file and create the proxy shown above. What am I doing wrong?

Arjuna

'nodemon' #24750895 – Adigun

You asked something similar here #35577163 – Specialistic

Is this an ExpressJS app? – Balmacaan

@threed yes. this is an expressjs app – Arjuna

what version of browsersync are you using? – Khadijahkhai

Answer 1

You actually don't need to use gulp for this to work.

a) restart my server when server-side code is changed

Install nodemon globally using npm i -g nodemon then on your app folder do nodemon or nodemon ${index-file-of-your-app}.

b) refresh the browser when client-side code is changes.

Use browserify or webpack. I prefer using webpack; you may need to learn about the configuration a little bit but the good thing with webpack is that you don't need to refresh it. Once changes are found the changes will be reflected on the browser automatically. https://github.com/webpack/docs/wiki/hot-module-replacement-with-webpack

Barratry

I have other things in my gulp file. That is why I want it in gulp. Is there a way to do it that is consistent with my question? – Arjuna

Can I see your gulp file or list the process/steps when running gulp? – Barratry

Answer 2

You can livereload both front and backend changes to the browser by using the 'livereload', 'connect-livereload', and 'nodemon' packages together. Also, this way you don't need Gulp or Grunt. Here's how the packages play together:

• livereload opens a high port and notifies the browser of changed public files
• connect-livereload monkey patches every served HTML page with a snippet that connects to this high port
• nodemon is then used to restart the server on changed backend files

Set up livereload in Express

Set up the Express to both start livereload server watching the public directory and ping the browser during nodemon-induced restart:

const livereload = require("livereload");
const connectLivereload = require("connect-livereload");

// open livereload high port and start to watch public directory for changes
const liveReloadServer = livereload.createServer();
liveReloadServer.watch(path.join(__dirname, 'public'));

// ping browser on Express boot, once browser has reconnected and handshaken
liveReloadServer.server.once("connection", () => {
  setTimeout(() => {
    liveReloadServer.refresh("/");
  }, 100);
});

const app = express();

// monkey patch every served HTML so they know of changes
app.use(connectLivereload());

Start Express with nodemon

Then you'd start the server with nodemon, for example, with a dedicated watch script by running npm run watch.

The key point here is to ignore the public directory that's already being watched by livereload. You can also configure files with non-default extensions, like pug and mustache, to be watched.

"scripts": {
  "start": "node ./bin/www",
  "watch": "nodemon --ext js,pug --ignore public"
},

You can read a longer explanation in "Refresh front and backend changes to browser with Express, LiveReload and Nodemon."

Olivaolivaceous

also do not use the command line provided here, use the command line already existing for the node execution such as -r esm index.js – Xuthus

Why is connect-livereload needed, I thought that livereload can watch html files without any further "support package"? Maybe it is needed here because you implemented livereload in server.js and not from the cmd with livereload . See docs – Billen

Answer 3

I might be missing some context (e.g. I'm not sure what input represents), however, I think the npm module reload might solve your problem. Here's an example from the npm package page:

var express = require('express')
  , http = require('http')
  , path = require('path')
  , reload = require('reload')
  , bodyParser = require('body-parser')
  , logger = require('morgan')

var app = express()

var publicDir = path.join(__dirname, '')

app.set('port', process.env.PORT || 3000)
app.use(logger('dev'))
app.use(bodyParser.json()) //parses json, multi-part (file), url-encoded  

app.get('/', function(req, res) {
  res.sendFile(path.join(publicDir, 'index.html'))
})

var server = http.createServer(app)

//reload code here 
//optional reload delay and wait argument can be given to reload, refer to [API](https://github.com/jprichardson/reload#api) below 
reload(server, app, [reloadDelay], [wait])

server.listen(app.get('port'), function(){
  console.log("Web server listening on port " + app.get('port'));
});

Balmacaan

Answer 4

@mateeyow is right.

But if you want the browser to reload automaticaly, you also need livereload-plugin.

Enable webpack-hot-replacement only replace code in browser's memory, livereload-plugin do reload it.

See rock for example: https://github.com/orange727/rock/blob/master/app/templates/webpack/webpack.make.js#L255

Just as:

webpackConfig.plugins: [
  new webpack.HotModuleReplacementPlugin(),
  new LiveReloadPlugin({
    appendScriptTag: true,
    port: config.ports.livereload,
})];

Wergild

Answer 5

The EADDRINUSE error is normally due to a connection already open on the specified port. This is probably due to a previous instance of the connection not being correctly closed when restarting the app.

Take a look at this gist and in particular try something like this in your gulp file:

'use strict';

var gulp = require('gulp');
var browserSync = require('browser-sync');
var nodemon = require('gulp-nodemon');

gulp.task('default', ['browser-sync'], function () {});

gulp.task('browser-sync', ['nodemon'], function() {
    browserSync.init(null, {
        proxy: "http://localhost:3002"
    });
});

gulp.task('nodemon', function (cb) {

    var started = false;

    return nodemon({
        script: 'app.js'
    }).on('start', function () {
        // to avoid nodemon being started multiple times
        if (!started) {
            cb();
            started = true; 
        } 
    });
});

Khadijahkhai