With Ken Powers Comes Ken Responsibility

Trying Out Node Modules

How do you try out node modules? Have you really thought about it at all? It’s something I’ve given some thought recently. Today’s post presents three options for trying out node modules with pros, cons, and recommended use cases for each.

Option 1: Install to a temporary project.

This is probably the most common method. It has existed since the dawn of time and will probably persist until the end of time because of its simplicity. Create and change to a new directory, npm i some stuff, and you’re off! There are two primary avenues for trying things out with this method: the node REPL and temporary scripts on disk executed via the node CLI. Use the REPL when you’re just trying out quick one-liners and use a script when you need to repeat and iterate on something a little more complex. What more needs to be said?


  • Simple. Nothing extra to install and it just works.
  • Use alternate REPLs (Babel, CoffeeScript, etc).
  • Flexibility in other ways to execute scripts (e.g., piping to stdin, passing JavaScript inline to -e, or using -r one or more times).
  • You are in complete control (node version, system tools, environment variables, etc).


  • Ceremony of multiple commands (mkdir -p, cd, npm, possibly other things).
  • Sharing anything requires a little extra work (creating a Gist, repo, etc).
  • You have to manually require modules if you want to access them by name.

Option 2: Tonic RunKit

Update 2016-09-15: Tonic is now known as RunKit.

You may have seen the following link in the sidebar on npm:


That’s a link to Tonic, a service which gives you notebooks to play around with node modules. These notebooks remind me a lot of Mathematica notebooks but with JavaScript instead of crazy math stuff. You can essentially think of them as node REPLs in your browser, with access to every version of every module on npm. You also get a host of other cool features, like data visualization, simple endpoint hosting, and the ability to share whatever you create. Additionally, module authors can declare examples for their modules directly in their package.json.

Tonic Data Visualization

Go ahead and click either screenshot above. They’ll take you to some pre-defined notebooks where you can play around. Better yet, I’ve embedded a notebook below where you can try out Lodash:

// Require everything, or you can `require` individual functions // See http://knpw.rs/blog/using-lodash const _ = require('lodash'); _.add(3, 5);



  • You have to wait on the server to evaluate your code. It isn’t terribly slow, but there is a noticeable delay.
  • No tab completion.

Option 3: repl’em

repl’em is basically a node REPL which lets you pre-install and require modules from its CLI. Want to try out moment? It’s this easy:

replem moment

You are dropped in to a REPL with a variable named moment available to you. Nice!

Want a REPL where Promise is actually bluebird? You can alias how modules will be exposed:

replem bluebird:Promise

repl’em also lets you use _ as an alias, which the default node REPL does not:

replem lodash:_

You can also install and use multiple modules all at once:

replem bluebird:Promise lodash:_ moment

And then you get some other stuff too, like using specific versions of modules, exposing modules’ properties, and custom REPLs (e.g., Babel, CoffeeScript, etc). See repl’em for more details.


  • Automatic camelCase conversion of kebab-case package names.
  • Tab completion works.
  • Simple interface.
  • Use alternate REPLs (Babel, CoffeeScript, etc).
  • Retains history of past sessions.


  • Global package to install and keep updated.
  • Cannot run scripts from disk (yet, as far as I can tell).

So what should I use?

This is just what works best for me, you should experiment and find out what works best for you. I’ve started using repl’em for my quick, one-off experiments in favor of installing things to a local directory. If I need something just a little more robust, however, like a quick script I’ll be iterating on, I’ll favor the temporary project directory. If I intend to share or embed something, I’ll lean towards Tonic.

Did I miss anything?

Well, yeah, probably. Feel free to post in the comments down below or reach out to me on Twitter to let me know your favorite way to try out node modules.

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