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Node.js – Auto Refresh In Dev

Posted by: admin November 29, 2017 Leave a comment

Questions:

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?

Answers:

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

Questions:
Answers:

I might be missing some context (e.g. I’m not sure what input represents), however, I think this npm module 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'));
});

Questions:
Answers:

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; 
        } 
    });
});

Questions:
Answers:

@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,
})];