A Note on npx

npx is the npm package executor. npx checks if an npm command exists in $PATH, or in the local project binaries, and then executes the command. If the command is not found, then the command will be installed using npm prior to its execution.

npx comes with npm installation v5.2.0 or later

# Stand-alone version of `npx`
npm install -g npx

npx is a tool for executing Node packages.

With npm, it is not possible to run any Node package without a run-script defined in package.json file.

# package.json
  "scripts": {
    "build": "gatsby build",
    "develop": "gatsby develop",
  }
...

$ cd project_directory/
$ npm run build

However, with npx, it is possible to run any Node package

npx gatsby build

You can run a Node package which was previously not installed on your machine.

npx create-react-app my-app

npx uses npm to install the Node packages into ~/.npm/_npx and adds them temporarily to $PATH

npm uninstall -g create-react-app
removed 114 packages in 2.233s

npx create-react-app task-manager
npx: installed 63 in 4.758s

Creating a new React app in /Users/klakum/Documents/Projects/task-manager.

Installing packages. This might take a couple of minutes.
Installing react, react-dom, and react-scripts...
...
Happy hacking!

While adding boilerplate for task-manager, you can actually see the create-react-app binary file cached at ~/.npm/_npx. This binary file and associated files are removed once npx completes its execution.

ls -alih ~/.npm/_npx/
ls ~/.npm/_npx/52147/bin/create-react-app 
/Users/klakum/.npm/_npx/52147/bin/create-react-app

You can run Node commands using different versions of the Node without installing them on your machine

npx node@v8.9.4 -v
v8.9.4

You can install npm dependencies for your project using a particular version of Node to verify backward compatibility of libraries

npx -p node@6 npm it

You can run npm scripts (defined in your project’s package.json) with specific Node version

npx -p node@8 npm run build

With npx, you will no longer need to install and use a Node version manager (nvm)

Examples

npx happy-birthday -u "Yaswin"
npx: installed 2 in 4.332s

🎂
పుట్టినరోజు శుభాకాంక్షలు Yaswin!
🎉


npx cowsay hello
npx: installed 10 in 9.553s
 _______
< hello >
 -------
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||

npx http-server
npx: installed 25 in 11.095s
Starting up http-server, serving ./
Available on:
  http://127.0.0.1:8080
  http://192.168.0.104:8080
Hit CTRL-C to stop the server

npx npm-check --skip-unused
npx: installed 247 in 9.048s

@uirouter/angularjs      😎  PATCH UP  Patch update available. https://ui-router.github.io
                                      npm install --save @uirouter/angularjs@1.0.20 to go from 1.0.13 to 1.0.20

angular                  😎  MINOR UP  Minor update available. http://angularjs.org
                                      npm install --save angular@1.7.5 to go from 1.5.8 to 1.7.5
...

Use npm-check -u for interactive update.

A Note on npx

Examples

Links