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hash-filename is a command line tool that puts the hash of a file into its filename.

Installation: npm install -g hash-filename

$ ls
app.css  app.js  vendor.js
hash-filename *.css *.js
$ ls
app-e242ed3bffc.js  app-f1d2d2f924e.css  app.css  app.js  vendor-6eadeac2dad.js  vendor.js
hash-filename --help
  Usage: hash-filename [options] <files>
    -h, --help              output usage information
    -V, --version           output the version number
    -a, --algorithm <name>  Hash algorithm [sha1]
    -l, --length <n>        Hash length [11]
Copies the given files with a hash of their contents put into to their filenames.
Writes a JSON map of original filenames to hashed filenames to stdout.

It is useful for cache busting. The outputted JSON map can be used to update references to the unhashed filenames.

For example, you could create a function such as the following, expose it to templates and wrap file paths in it.

var map = production ? require("./map") : {} // You can even require .json files! 
function file(path) {
  return map[path] || path

The above function uses the original paths during development and the hashed ones during production. And if for some reason a path would be missing from the map during production, it falls back to the original path.

You could also feed the map directly to a replacement tool such as map-replace to update static files:

hash-filename *.css *.js | map-replace -m "<[^>]+>" *.html