What interesting things I can do with npm?

This thread made me think that I want to get a better grasp of what I can do through npm:

I knew about this feature and more or less know all the npm features, but I still feel a bit out of the loop about the ways people are using this tech/service. Care to fill me in on how you make use of the npm service and ecosystem?

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  1. NPM scripts - they automatically add "./node_modules/.bin" to your PATH when they are executed, so if you have mocha installed, for example, your NPM script can just be ..."test": "mocha ..."...
  2. NPX - use npx to run scripts in "./node_modules/.bin": npx mocha ... for one-off commands; if NPX cannot find the binary there, it will temporarily download it!
    • npx create-react-app is awesome
  3. npm ci - look it up it's pretty cool
  4. Use "devDependencies", and use it correctly!
  5. Use the "prepack" hook to run tests & build before your module is built!
  6. "npm pack" will build the *.tgz that NPM stores on their public registry. In many ways this is akin to Java WAR files, without all of the dependencies. You can then put this *.tgz on your server and do an "npm install my-package-0.0.1.tgz"
  7. "bundleDependencies" - worth knowing about (also a tool to use with it is: bundle-deps; run with "npx bundle-deps")

One of my pet-peeves is when a package is globally installed when it should be a devDependencies within a project. For example, if you use the TypeScript compiler in a project, "typescript" is a "devDependency"; do not make installing it globally a requirement. This lets different projects depend on different versions of the typescript compiler. It also makes it so that somebody can download your project and run a build without having to install additional dependencies. This goes for gulp, etc.

I also forgot a few:

  • npm link - useful if you depend on a development version of a package that only exists on your local machine
  • npm install /path/to/file - alternative way to accomplish the above point: recent versions of NPM just create a symlink! so you can edit the linked project live and have updates just like you would expect
  • npm audit - available in >=v6.x - runs a security audit on your dependencies
  • npm info - want to see what version of a package is the latest? Run npm info express dist-tags
  • npm install github.com/user/project#semver:^1.0.0
  • npm install some-package@next - install not the "latest" version, but the version tagged by "next"

NPM greater than version 5 is pretty amazing. Earlier versions, not so much. I would recommend yarn if you are stuck with earlier versions of NPM.

Oh, and don't forget that an .npmrc file local to your project overrides a global .npmrc file: useful for CI servers (store a .npmrc file with your project)!

Good point on the project specific .npmrc.

Another tip is that a separate repository (and credentials) can be configured per scope as well (credit Guillaume Martigny for mentioning scoped modules first below).


This can be useful if you have some private modules in a private repository but do not wish to proxy all requests for public modules through it as well.

I also agree npm link is very useful if working on multiple modules and testing fixes.

My last uses of the npm were

  • lose 3 days to make a project work (because of x dependencies random errors)
  • spend hours and hours to "debug" errors like "undefined"
  • eat popcorn while browsing NPM's source and see how to not write code

Savage! But then, this truly reflects on the state of JavaScript: very popular, and very messy.

One thing that comes to mind: you can use npm + unpkg to publish websites 😁

Here's one not a lot of people know about.

npx comes bundled with npm 5.2.0+. It temporarily downloads then executes an npm package that's used as a script (such as create-react-app) without needing to install it anywhere on the machine.

A fun example if you want to try it out is cowsay, a little script that outputs an ASCII cow saying something:

> npx cowsay "Cows are the silent jury in the trial of mankind."
/ Cows are the silent jury in the trial of \
\  mankind.                                /
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||

Fantastic! Thanks for sharing Shawn!

I abuse the heck out of npm scripts. They aren't just for build, serve, and test!

For instance, as a SQA, I need to have packages like Jasmine and Protractor, and then use Protractor to kick off my tests and maintain my selenium package.

So in my package.json, I include in scripts:

  "scripts": {
    // snip
    "update-webdriver": "node node_modules/protractor/node_modules/webdriver-manager/bin/webdriver-manager update",
    "preprotractor": "npm run update-webdriver",
    "protractor": "node node_modules/protractor/bin/protractor path/to/conf/file",
    // snip

So what happens when I run npm run protractor is:

  1. I get the latest selenium jar and chromedriver (and other drivers I don't care about like gecko but whatever)
  2. The local installation of protractor kicks off a test run with the default suite.

Things this buys me:

  1. Every single guide on protractor starts with npm i -g protractor. NO. Bad. I don't want every onboarding to be a laundry list of global packages to install. Just use project dev-dependencies and scripts that alias the unweildy bin paths. Now everyone's computers can be happy cookie cutters without needing local aliasing and global installs.
  2. Since scripts has a concept of pre and post runs, I can ensure everyone actually keeps chromedriver up to date with Chrome without having to keep tabs on that. It just works
  3. I can still override or include settings at runtime like npm run protractor -- --suite=api rather than always using the default.

I'm half tempted to put in a postprotractor for running npm run eslint -- --fix e2e-tests/** but I might hear complaints if I do that...

But I do this set up on every project I'm on to keep things nice and tidy.

Worth noting that you don't need to write node node_modules/.bin/protractor config - you can just use protractor config and npm will figure out the rest for you :)

Nifty! I'll try to remember that next time.

Don't want to be too much showy, but sub-packages are cool.

Basically, inside one repo, you have a main package that depend on smaller package. Check Pencil.js for a real-life example.
You don't have to use scoped packages, but I would recommend it.

Thanks to Lerna managing the whole thing is pretty easy.

  1. Use npm pack <packagename> to download tgz file of what gets installed on your machine.
  2. Use npm view <packagename> to view the package.json of the package.

Checking if packages are up-to-date, I sometimes npm outdated to list packages' current version used, wanted version and latest version.

I use npm scripts to compile Pug and Sass, build my Hugo site, and optimize images. My Sam Hugo theme does something similar, without the images though.

Hey, lots of handy stuff in the comments but I noticed nobody has mentioned this yet. You can host your own NPM server and configure NPM to use your-registry.com in stead.

There are various packages on NPM itself (such as verdaccio) that offer a NPM server. Some are minimal, other are fully featured. You can use a custom NPM server not only to make your packages private (to your team) but also to serve as proxy, or have it fallback to NPM when your registry has no package by the name of what is being queried.

Best thing is that dev-dependencies are accessible like globals in npm scripts.

So you can run "npm i" and then simply run every script and use global packages without installing them globally.

Quick one: I recently made fastjs.link as a short linking service that links directly to the homepage of an npm package. Pretty useful for blogging on dev.to, actually!

Classic DEV Post from Oct 12 '17

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Ben Halpern
A Canadian software developer who thinks he’s funny.
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