Using watch and glob - package.json example

.watch.js

var glob = require('glob');
var path = require('path');

// ===== files to watch =====
// this is just a simple glob example that could be done far more
// easily by using the following run script in package.json:
// "watch": "watch '<cmd>' ./src"

var pattern = './src/**/*';
var options = {};
// ==========================

var files = glob.sync(pattern, options);
var set = new Set();

// Add all the files we want to watch to the set.
// We need to explicitly add the directory name
// to the set as well, otherwise the watch
// filter function won't watch files in it.
files.forEach(function(f) {
  var p = path.relative(__dirname, f);
  set.add(p);
  var dir = path.parse(p).dir;
  set.add(dir);
});


// Exports a filter function that returns true or false for each file and
// directory to decide whether or not that file or directory is included by
// watch. The argument to the function (f) is a fully qualified string pathname.
module.exports = function(f) {
  // The original naive approach attempted to use minimatch, but minimatch
  // rejects 'src' when the glob pattern is 'src/**', for example, and if
  // the 'src' dir is rejected, watch won't call this filter function with
  // any files inside the 'src' directory.
  // This is an artificial example, but reflects my desire to handle
  // simple glob patterns that might be supplied by a user that should
  // work as expected.
  var p = path.relative(__dirname, f);
  var watch = set.has(p);
  if (watch) console.log(p);
  return set.has(p);
};

package.json

{
  "name": "node-app",
  "version": "1.0.0",
  "scripts": {
    "watch": "watch 'npm run build' --wait=1 --filter=./.watch.js",
    "build": "echo building..."
  },
  "devDependencies": {
    "glob": "^6.0.4",
    "watch": "^0.17.1"
  }
}