node-dev (1)

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 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.

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 require a .json file or a .ts script for example and it will be watched. Automatically.

Usage

Just run node-dev as you would normally run node:

node-dev server.js

TypeScript support

You can use node-dev to watch and restart TypeScript projects. Install ts-node as dev-dependency, then use node-dev to run your script:

node-dev src/server.ts

Command-line options

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
• --deps:
  • -1 - Watch the whole dependency tree
  • 0 - Watch only the project's own files and linked modules (via npm link)
  • 1 (Default) - Watch all first level dependencies
  • <number> - Number of levels to watch
• --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=false - Disable 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

Passing arguments to node

All command-line arguments that are no node-dev options are passed on to the node process.

Installation

node-dev can be installed via npm. Installing it with the -g option will allow you to use it anywhere you would use node.

npm install -g node-dev

Desktop Notifications

Status and error messages can be displayed as desktop notification using node-notifier:

Requirements:

• Mac OS X: >= 10.8
• Linux: notify-osd or libnotify-bin installed (Ubuntu should have this by default)
• Windows: >= 8, or task bar balloons for Windows < 8

Config file

Upon startup node-dev looks for a .node-dev.json file in the following directories:

• the user's home directory
• the current working directory
• the same directory as the script to run

Settings found later in the list will overwrite previous options.

Configuration options

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: false
• dedupe – Whether modules should by dynamically deduped. Default: false
• deps – How many levels of dependencies should be watched. Default: 1
• fork – Whether to hook into child_process.fork (required for clustered programs). Default: true
• graceful_ipc - Send the argument provided as an IPC message instead of SIGTERM during restart events. Default: "" (off)
• ignore - A single file or an array of files to ignore. Default: []
• notify – Whether to display desktop notifications. Default: true
• poll - Force polling for file changes, this can be CPU-heavy. Default: false
• respawn - Keep watching for changes after the script has exited. Default: false
• timestamp – The timestamp format to use for logging restarts. Default: "HH:MM:ss"
• vm – Whether to watch files loaded via Node's VM module. Default: true

ESModules

When using ESModule syntax and .mjs files, node-dev will automatically use a loader to know which files to watch.

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 app.

Transpilers

You can use node-dev to run transpiled languages like TypeScript. You can either use a .js file as entry point to your application that registers your transpiler as a require-extension manually, for example by calling CoffeeScript.register() or 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 the map looks like this:

{
  "coffee": "coffee-script/register",
  "ls": "LiveScript",
  "ts": "ts-node/register"
}

This means that if you run node-dev server.ts node-dev will do a require("ts-node/register") before running your script. You need to have ts-node installed as a dependency of your package.

Options can be passed to a transpiler by providing an object containing name and options attributes:

{
  "js": {
    "name": "babel-core/register",
    "options": {
      "only": ["lib/**", "node_modules/es2015-only-module/**"]
    }
  }
}

Graceful restarts

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 SIGTERM cause 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 via child.send("<graceful_ipc argument>"). The child process can listen and handle this event with:

process.on('message', function (msg) {
  if (msg === '<graceful_ipc argument>') {
    // Gracefully shut down here
    doGracefulShutdown();
  }
});

Ignore paths

If you’d like to ignore certain paths or files from triggering a restart, list them in the .node-dev.json configuration under "ignore" like this:

{
  "ignore": ["client/scripts", "shared/module.js"]
}

This can be useful when you are running an isomorphic web app that shares modules between the server and the client.

License

MIT