npx

Overview

• npx on NPM

  execute npm package binaries

It is not a subcommand of npm. It already comes with npm (at least newer versions) and works well with the NPM ecosystem.

Usage

$ npx NODE_PACKAGE OPTIONS

From the help:

npx [options] <command>[@version] [command-arg]...

npx [options] [-p|--package <pkg>]... <command> [command-arg]...

npx [options] -c '<command-string>'

npx --shell-auto-fallback [shell]

e.g.

$ npx prettier --help
$ npx prettier -w .

Purpose

Run installed package

Executes <command> either from a local node_modules/.bin, or from a central cache, installing any packages needed in order for <command> to run.

By default, npx will check whether exists in $PATH, or in the local project binaries, and execute that.

For example, install a package in a project:

$ npm install eslint

$ # Run with:
$ ./node_modules/.bin/eslint
$ # OR
$ npx eslint

Or globally:

$ npm install --global eslint

$ eslint
$ # OR
$ /usr/local/bin/eslint

Then use NPX to run it, either from in your project or from anywhere (if globally installed):

$ npx eslint --help
$ npx eslint .

Run package not installed

If <command> is not found, it will be installed prior to execution.

Run any package that is available on NPM, without installing it first.

$ npx eslint

If you run the command above again, it will download a fresh copy of the package and then run it. It will not cache it.

This can be frustrating if you have to run the command a few times in a row.

issue

There is discussion in that issue and the docs arouch using a cache directory, but that might just reading from NPM’s cache and it doesn’t seem to write to it.

Keep global packages clean

NPX does not leave behind any permanent affects.

If you install a lot of packages in you global NPM directory using npm i -g, then you would “pollute” the NPM bin directory in your PATH. So there are more commands to look through and accidentally run when running a command anywhere.

reference

Common uses

NPX is great for one-off commands where you don’t plan to reuse the package. And if you always want to run the latest version (you don’t have to worry if you installed package is outdated).

Bootstrap projects

When you want to scaffold a new app.

React:

$ npx create-react-app my-app

Neutrino:

$ npx @neutrinojs/create-project my-app

Format

Download and run Prettier against your project.

$ npx prettier -w .

Test commands

Run an ad hoc command for experimenting with arguments. In Vue, you’ll typicall have vue-cli-service installed directly and access it through npm run COMMAND, but you might want to explore the CLI using npx.

$ npx vue-cli-service --help

$ npx vue-cli-service serve

Before adding to your package.json file.

{
  "scripts": {
    "serve": "vue-cli-service serve",
  }
}

$ npm run serve

vue docs