Node-dev is a development tool for Node.js that automatically restarts the node process when a file is modified.
In contrast to tools like
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.
This means that you don't have to configure any include- or exclude rules. If you modify a JS file that is solely used on the client-side but never run on the server, node-dev will know this and won't restart the process.
This also means that you don't have to configure any file extensions. Just
.json file or a
.coffee script for example and it will be watched.
Node-dev uses filewatcher under
the hood and hence will take advantage of the native
fs.watch() API if it
is available on your system.
node-dev as you would normally run
There are a couple of command line options that can be used to control which files are watched and what happens when they change:
--clear- Clear the screen on restart
--dedupe- Dedupe dynamically
- -1 - Watch the whole dependency tree
- 0 - Watch only the project's own files and linked modules (via
- 1 (Default) - Watch all first level dependencies
--fork- Hook into child_process.fork
--graceful_ipc <msg>- Send 'msg' as an IPC message instead of SIGTERM for restart/shutdown
--ignore- A file whose changes should not cause a restart
--notify- Display desktop notifications
--poll- Force polling for file changes (Caution! CPU-heavy!)
--respawn- Keep watching for changes after the script has exited
--timestamp- The timestamp format to use for logging restarts
--vm- Load files using Node's VM
By default node-dev will watch all first-level dependencies, i.e. the ones in
Node-dev can be installed via npm. Make sure to use the
-g option to install
npm install -g node-dev
Status and error messages can be displayed as desktop notification using node-notifier:
- Mac OS X: >= 10.8 or Growl if earlier.
- Linux: notify-osd installed (Ubuntu should have this by default)
- Windows: >= 8, task bar balloon if earlier or Growl if that is installed.
- General Fallback: Growl
Usually node-dev doesn't require any configuration at all, but there are some options you can set to tweak its behaviour:
clear– Whether to clear the screen upon restarts. Default:
dedupe– Whether modules should by dynamically deduped. Default:
deps– How many levels of dependencies should be watched. Default:
fork– Whether to hook into child_process.fork (required for clustered programs). Default:
graceful_ipc- Send the argument provided as an IPC message instead of SIGTERM during restart events. Default:
ignore- A single file or an array of files to ignore. Default:
notify– Whether to display desktop notifications. Default:
poll- Force polling for file changes, this can be CPU-heavy. Default:
respawn- Keep watching for changes after the script has exited. Default:
timestamp– The timestamp format to use for logging restarts. Default:
vm– Whether to watch files loaded via Node's VM module. Default:
Upon startup node-dev looks for a
.node-dev.json file in the following directories:
- user's HOME directory
- the current working directory (as provided by process.cwd())
- the same directory as the script to be run
Settings found later in the list will overwrite previous options.
Dedupe linked modules
Sometimes you need to make sure that multiple modules get
exactly the same instance of a common (peer-) dependency. This can usually be
achieved by running
npm dedupe – however this doesn't work when you try to
npm link a dependency (which is quite common during development). Therefore
node-dev provides a
--dedupe switch that will inject the
dynamic-dedupe module into your
You can also use node-dev to run transpiled languages. You can either use a
.js file as entry point to your application that registers your transpiler as
require-extension manually, for example by calling
you can let node-dev do this for you.
There is a config option called
extensions which maps file extensions to
compiler module names. By default this map looks like this:
This means that if you run
node-dev foo.coffee node-dev will do a
require("coffee-script/register") before running your script.
Note: If you want to use coffee-script < 1.7 you have to change the
Options can be passed to a transpiler by providing an object containing
Node-dev sends a
SIGTERM signal to the child-process if a restart is required.
If your app is not listening for these signals
process.exit(0) will be called
immediately. If a listener is registered, node-dev assumes that your app will
exit on its own once it is ready.
Windows does not handle POSIX signals, as such signals such as
the process manager to unconditionally terminate the application with no chance
of cleanup. In this case, the option
graceful_ipc may be used. If this option
is defined, the argument provided to the option will be sent as an IPC message
child.send("<graceful_ipc argument>"). The child process can listen and
handle this event with:
If you’d like to ignore certain paths or files from triggering a restart simply
list them in the
.node-dev.json configuration under
This might be useful when you are running a universal (isomorphic) web app that shares modules across the server and client, e.g. React.js components for server-side rendering, which you don’t want to trigger a server restart when changed, since it introduces an unnecessary delay.