Create Your First Command

Table of contents

Run from a script file
Run from a package
- Global level
- Working directory

Table of contents

Run from a script file
Run from a package
- Global level
- Working directory

In this guide, you will learn how to build and run your own command.

Run from a script file

In your favorite editor, create a hello-world.js file.

function helloWorld () {
  console.log('Hello World');
}
// expose the function to be required later
module.exports = helloWorld;

To run the script file, navigate in the right folder using cd() and ls().

> ls()
[ 'hello-world.js' ]
> hello = require(path.resolve('hello-world.js'))
[Function: helloWorld]
> hello()
Hello World
undefined

Voilà, the script prints Hello World in the stdout. Notice undefined, which is the returned value of the function.

Run from a package

In many cases, scripts are released in a package. A package is a file or directory that is described by a package.json file. This file gives information about the package itself such as its name, its authors, its version but also how to interact with it, how to publish it, etc. More information about how to create a Node.js module here.

To run a script from a package, you must have it installed at a global level or in the current working directory.

Global level

> $('npm install --global hellonacre')
'\nadded 1 package, and audited 2 packages in 430ms\n\nfound 0 vulnerabilities\n'
> hellonacre()
Hello World
undefined

Working directory

// init package.json with empty config
> cat.append('package.json', '{}')
'{}'
// install hellonacre package in the working directory
> $('npm install hellonacre')
'\n' +
  'added 1 package, and audited 3 packages in 1s\n' +
  '\n' +
  '1 package is looking for funding\n' +
  '  run `npm fund` for details\n' +
  '\n' +
  'found 0 vulnerabilities\n'
// check if the package is present in node_modules folder
> ls('node_modules/')
[ 'node_modules/.package-lock.json', 'node_modules/hellonacre' ]
> hellonacre()
Hello World
undefined