How to auto-reload files in Node js

Question

Any ideas on how I could implement an auto-reload of files in Node js  I m tired of restarting the server every time I change a file   Apparently Node js  require   function does not reload files if they already have been required  so I need to do something like this   var sys       require  sys         http      require  http        posix     require  posix        json      require    json     var script name     some path to app js   this app   require    app   app   process watchFile script name  function curr  prev       posix cat script name  addCallback function content           process compile  content  script name                 http createServer this app  listen  8080      And in the app js file I have   var file   require    file    this app   function req  res         file serveFile  req  res   file js          But this also isn t working - I get an error in the process compile   statement saying that  require  is not defined  process compile is evaling the app js  but has no clue about the node js globals

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Use this   function reload config file      if    this instanceof reload config       return new reload config file     var self   this     self path   path resolve file      fs watchFile file  function curr  prev        delete require cache self path         extend self  require file               extend self  require file        All you have to do now is   var config   reload config    config      And config will automatically get reloaded

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my app structure   NodeAPP  folder      -- app  folder         -- all other file is here     -- node modules  folder      -- package json     -- server js  my server file    first install reload with this command   npm install  -g   --save-dev  reload   then change package json    scripts          start    nodemon -e css ejs js json --watch app      now you must use reload in your server file   var express   require  express    var reload   require  reload    var app   express     app set  port   process env PORT    3000    var server   app listen app get  port    function         console log   server is running on port     app get  port          reload server  app     and for last change  end of your response send this script    lt script src   reload reload js  gt  lt  script gt    now start your app with this code   npm start

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nodemon came up first in a google search  and it seems to do the trick   npm install nodemon -g cd whatever dir holds my app nodemon app js

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Not necessary to use nodemon or other tools like that  Just use capabilities of your IDE    Probably best one is IntelliJ WebStorm with hot reload feature  automatic server and browser reload  for node js

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yet another solution for this problem is using forever     Another useful capability of Forever is that it can optionally restart   your application when any source files have changed  This frees you   from having to manually restart each time you add a feature or fix a   bug  To start Forever in this mode  use the  -w flag     forever -w start server js

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You can use nodemon from NPM  And if you are using Express generator then you can using this command inside your project folder   nodemon npm start   or using Debug mode  DEBUG yourapp   nodemon npm start   you can also run directly  nodemon your-app-file js   Hope this help

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I have tried pm2   installation is easy and easy to use too  the result is satisfying  However  we have to take care of which edition of pm2 that we want  pm 2 runtime is the free edition  whereas pm2 plus and pm2 enterprise are not free   As for Strongloop  my installation failed or was not complete  so I couldn t use it

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You can use auto-reload to reload the module without shutdown the server   install  npm install auto-reload   example  data json     name     Alan      test js  var fs   require  fs    var reload   require  auto-reload    var data   reload    data   3000      reload every 3 secs     print data every sec setInterval function         console log data      1000       update data json every 3 secs setInterval function         var data       name       Math random                fs writeFile    data json   data      3000     Result     name   Alan      name   Alan      name   Alan      name   Alan      name   Alan      name   0 8272748321760446      name   0 8272748321760446      name   0 8272748321760446      name   0 07935990858823061      name   0 07935990858823061      name   0 07935990858823061      name   0 20851597073487937      name   0 20851597073487937      name   0 20851597073487937

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There is Node-Supervisor that you can install by  npm install supervisor   see http   github com isaacs node-supervisor

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i found a simple way   delete require cache   home shimin test2 js

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I recently came to this question because the usual suspects were not working with linked packages  If you re like me and are taking advantage of npm link during development to effectively work on a project that is made up of many packages  it s important that changes that occur in dependencies trigger a reload as well    After having tried node-mon and pm2  even following their instructions for additionally watching the node modules folder  they still did not pick up changes  Although there are some custom solutions in the answers here  for something like this  a separate package is cleaner  I came across node-dev today and it works perfectly without any options or configuration   From the Readme      In contrast to tools like supervisor or nodemon it doesn t scan the filesystem for files to be watched  Instead it hooks into Node s require   function to watch only the files that have been actually required

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node-dev works great  npm install node-dev  It even gives a desktop notification when the server is reloaded and will give success or errors on the message   start your app on command line with   node-dev app js

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solution at   http   github com shimondoodkin node-hot-reload  notice that you have to take care by yourself of the references used   that means if you did   var x require  foo    y x z x bar  and hot reloaded it   it means you have to replace the references stored in x  y and z  in the hot reaload callback function   some people confuse hot reload with auto restart my nodejs-autorestart module also has upstart integration to enable auto start on boot  if you have a small app auto restart is fine  but when you have a large app hot reload is more suitable  simply because hot reload is faster   Also I like my node-inflow module

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Nowadays WebPack dev server with hot option is used   you can add a script like this in your package json    hot    cross-env NODE ENV development webpack-dev-server --hot --inline --watch-poll     and every change in your files will trigger a recompile automatically

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Here is a blog post about Hot Reloading for Node  It provides a github Node branch that you can use to replace your installation of Node to enable Hot Reloading   From the blog   var requestHandler   require    myRequestHandler     process watchFile    myRequestHandler   function        module unCacheModule    myRequestHandler      requestHandler   require    myRequestHandler       var reqHandlerClosure   function  req  res      requestHandler handle req  res      http createServer reqHandlerClosure  listen 8000        Now  any time you modify myRequestHandler js  the above code will no  tice and re  place the local re  questHandler with the new code  Any ex  ist  ing re  quests will con  tin  ue to use the old code  while any new in  com  ing re  quests will use the new code  All with  out shut  ting down the serv  er  bounc  ing any re  quests  pre  ma  ture  ly killing any re  quests  or even re  ly  ing on an in  tel  li  gent load bal  ancer

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Here s a low tech method for use in Windows  Put this in a batch file called serve bat    echo off   serve start  wait node exe    goto  serve   Now instead of running node app js from your cmd shell  run serve app js   This will open a new shell window running the server  The batch file will block  because of the  wait  until you close the shell window  at which point the original cmd shell will ask  Terminate batch job  Y N    If you answer  N  then the server will be relaunched   Each time you want to restart the server  close the server window and answer  N  in the cmd shell

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For people using Vagrant and PHPStorm  file watcher is a faster approach   disable immediate sync of the files so you run the command only on save then create a scope for the   js files and working directories and add this command   vagrant ssh -c   var www gadelkareem com forever sh restart    where forever sh is like     bin bash  cd  var www gadelkareem com   amp  amp  forever  1 -l  var www gadelkareem com  tmp log forever log -a app js

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another simple solution is to use fs readFile instead of using require you can save a text file contaning a json object  and create a interval on the server to reload this object   pros    no need to use external libs relevant for production  reloading config file on change  easy to implement   cons    you can t reload a module - just a json containing key-value data

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You can do it with browser-refresh  Your node app restarts automatically  your result page in browser also refreshes automatically  Downside is that you have to put js snippet on generated page  Here s the repo for the working example   const http   require  http    const hostname    localhost   const port   3000   const server   http createServer  req  res    gt        res statusCode   200      res setHeader  Content-Type    text html  charset UTF-8        res write  Simple refresh         res write   lt script src   process env BROWSER REFRESH URL  gt  lt  script gt         res end        server listen port  hostname       gt        console log  Server running at http     hostname    port           if  process send            process send   event   online   url   http     hostname    port

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nodemon is a great one  I just add more parameters for debugging and watching options   package json     scripts          dev    cross-env NODE ENV development nodemon --watch server --inspect   server server js        The command  nodemon --watch server --inspect   server server js  Whereas   --watch server Restart the app when changing  js   mjs   coffee   litcoffee  and  json files in the server folder  included subfolders    --inspect Enable remote debug     server server js The entry point   Then add the following config to launch json  VS Code  and start debugging anytime          type    node        request    attach        name    Attach        protocol    inspector        port   9229     Note that it s better to install nodemon as dev dependency of project  So your team members don t need to install it or remember the command arguments  they just npm run dev and start hacking   See more on nodemon docs  https   github com remy nodemon monitoring-multiple-directories

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const cleanCache    moduleId    gt        const module   require cache moduleId       if   module            return               1  clean parent     if  module parent            module parent children splice module parent children indexOf module   1                2  clean self     require cache moduleId    null

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A good  up to date alternative to supervisor is nodemon      Monitor for any changes in your node js application and automatically restart the server - perfect for development   To use nodemon     npm install nodemon -g   nodemon app js

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node-supervisor is awesome  usage to restart on save    npm install supervisor -g supervisor app js   by isaacs - http   github com isaacs node-supervisor

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If somebody still comes to this question and wants to solve it using only the standard modules I made a simple example   var process   require  process    var cp   require  child process    var fs   require  fs     var server   cp fork  server js    console log  Server started     fs watchFile  server js   function  event  filename        server kill        console log  Server stopped        server   cp fork  server js        console log  Server started         process on  SIGINT   function          server kill        fs unwatchFile  server js        process exit          This example is only for one file  server js   but can be adapted to multiple files using an array of files  a for loop to get all file names  or by watching a directory   fs watch       function  event  filename       sub directory changes are not seen     console log  restart server        server kill        server   cp fork  server js             This code was made for Node js 0 8 API  it is not adapted for some specific needs but will work in some simple apps   UPDATE  This functional is implemented in my module simpleR  GitHub repo

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Edit  My answer is obsolete  Node js is a very fast changing technology   I also wondered about reloading modules  I modified node js and have published the source at Github at nalply node  The only difference is the function require  It has an optional second argument reload   require url  reload    To reload app js in current directory use  app   require    app   true     Write something like this  and you have auto-reload   process watchFile script name  function curr  prev        module   reload script name  true         The only problem I see is the variable module  but I am working at it now

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loaddir is my solution for quick loading of a directory  recursively   can return      path to file    fileContents       or    path    to    file   fileContents        It has callback which will be called when the file is changed   It handles situations where files are large enough that watch gets called before they re done writing   I ve been using it in projects for a year or so  and just recently added promises to it   Help me battle test it   https   github com danschumann loaddir

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I am working on making a rather tiny node  thing  that is able to load unload modules at-will  so  i e  you could be able to restart part of your application without bringing the whole app down   I am incorporating a  very stupid  dependency management  so that if you want to stop a module  all the modules that depends on that will be stopped too   So far so good  but then I stumbled into the issue of how to reload a module  Apparently  one could just remove the module from the  require  cache and have the job done  Since I m not keen to change directly the node source code  I came up with a very hacky-hack that is  search in the stack trace the last call to the  require  function  grab a reference to it s  cache  field and  well  delete the reference to the node        var args   arguments     while  args  1       args  1   cache            args   args callee caller arguments           var cache   args  1   cache     util log  remove cache     moduleFullpathAndExt      delete  cache  moduleFullpathAndExt        Even easier  actually   var deleteCache   function moduleFullpathAndExt      delete  require cache  moduleFullpathAndExt         Apparently  this works just fine  I have absolutely no idea of what that arguments  1   means  but it s doing its job  I believe that the node guys will implement a reload facility someday  so I guess that for now this solution is acceptable too   btw  my  thing  will be here  https   github com cheng81 wirez   go there in a couple of weeks and you should see what I m talking about

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There was a recent thread about this subject on the node js mailing list   The short answer is no  it s currently not possible auto-reload required files  but several people have developed patches that add this feature

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