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How to make beautiful, simple CLI apps with Node

Channel your inner Sindre Sohrus and ship a beautifully simple CLI app using Node.

Command line apps are a neat way to package repetitive tasks. This will walk you through some tools that are useful to build CLI apps.

Table of Contents

The idea 💡

When merging/rebasing, the file that always seems to cause trouble is the package-lock. We’ll go through how to make a simple utility that deletes the package-lock.json file, regenerates it (npm install) and adds it to the git index.

You can find it here: https://github.com/HugoDF/fix-package-lock and run it using npx fix-package-lock.

Piping to the command line 🚇

To start off, we’ll leverage a package from Sindre Sohrus, execa, which is described as “a better child_process”. For the following snippet to work, run npm install --save execa:

index.js

const execa = require('execa');

execa('ls').then(result => console.log(result.stdout));
node index.js
index.js
node_modules
package-lock.json
package.json 

Dealing with sequential actions ✨

To re-generate the package-lock we’ll need to first delete it, then run an npm install.

To this end, we can use Listr, it allows us to do things that look like:

Run npm install --save listr and add leverage Listr as follows:

index.js:

const execa = require('execa');
const Listr = require('listr');

new Listr([
  {
    title: 'Removing package-lock',
    task: () => execa('rm', ['package-lock.json'])
  },
  {
    title: 'Running npm install',
    task: () => execa('npm', ['install'])
  },
  {
    title: 'Adding package-lock to git',
    task: (ctx, task) =>
        execa('git', ['add', 'package-lock.json'])
        .catch(() => task.skip())
  }
]).run();

Now the output of node index.js looks like the following: `node index.js` output

Listr gives you a loading state when you have a long-running task that returns a Promise (like the execa invocation of npm install).

It’s also possible to display a message that changes using Observables, for more information see the Listr docs

Executable JavaScript files 🦅

It’s ideal to be able to execute our script using ./index.js instead of node index.js.

To do this, we need the file to be executable on UNIX systems that’s: chmod +x. So

chmod +x index.js

We then need to inform the system how it should attempt to run the file, that’s using the following hashbang:

#!/usr/bin/env node

If we add it to index.js we get:

#!/usr/bin/env node
const execa = require('execa');
const Listr = require('listr');

new Listr([
  {
    title: 'Removing package-lock',
    task: () => execa('rm', ['package-lock.json'])
  },
  {
    title: 'Running npm install',
    task: () => execa('npm', ['install'])
  },
  {
    title: 'Adding package-lock to git',
    task: (ctx, task) =>
        execa('git', ['add', 'package-lock.json'])
        .catch(() => task.skip())
  }
]).run();

Which we can now run using:

./index.js

Adding package binaries

npm has a bin field which we can use like the following (in package.json):

{
  "name": "beautiful-cli",
  "version": "1.0.0",
  "description": "A simple CLI",
  "main": "index.js",
  "bin": {
    "fix-package-json": "./index.js"
  }
  "dependencies": {
    "execa": "^0.10.0",
    "listr": "^0.14.1"
  }
}

Publishing to npm 🚀

This is left to the reader as an exercise, although using the np package, it’s super straightforward.

Hint: run npx np in whatever package you’re trying to publish

You can find the full package at You can find it here: https://github.com/HugoDF/fix-package-lock and run it using npx fix-package-lock.

Author

Hugo Di Francesco

Co-author of "Professional JavaScript" with Packt. He runs the Code with Hugo website helping over 100,000 developers every month and holds an MEng in Mathematical Computation from University College London (UCL). He has used JavaScript extensively to create scalable and performant platforms at companies such as Canon and Elsevier.

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