How to Create a Node.js CLI Project

JavaScript is now the most popular programming language. Node.js is no longer limited to web development but also allows us to develop command line applications, CLI, or server side applications with JavaScript. This article will explain how to create a Node.js CLI project.

Creating a Node.js Project

First, create a folder, execute npm init -y under the folder, and a project is created! You can see a package.json file is generated under the folder. It is the configuration file of a Node.js project.

% mkdir hello-cli
% cd hello-cli
% npm init -y
% ls
package.json

Let’s take a quick look at package.json.

• name: Project name
• version: Project version
• main: The entry file of the project. The default file is index.js, but NPM will not automaitcally generate it.

{
  "name": "hello-cli",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC"
}

Creating a Node.js CLI Script

Create an index.js file and fill in the code below. The first line tells the OS to execute this script file with node command.

#!/usr/bin/env node

const [,, ... args] = process.argv;
console.log(`Hello ${args}`);

Let’s execute index.js. Set index.js as an executable file, and execute it.

hello-cli % chmod +x index.js
hello-cli % ./index.js Wayne
Hello Wayne

Setting Project’s CLI

The  main in package.json is the entry point when other projects import hello-cli. But hello-cli is a CLI project, not a Node.js module project, so we can remove it.

We add a property named bin in package.josn, and add a property named hello under the bin. This hello is a CLI command executing index.js. After users install hello-cli, they can run hello under the command line.

{
  "name": "hello-cli",
  "version": "1.0.0",
  "description": "",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "bin": {
    "hello": "index.js"
  }
}

Installing a CLI Project to the Local System

We just created hello command, but without installing the project, we cannot test it. However, we also don’t want to test our project by directly executing index.js.

Under the project folder, we can install the project to the local system by executing npm link.

hello-cli % npm link

Then you can execute the project locally.

% hello Wayne
Hello Wayne

Use the following command to uninstall it from the local sytem.

hello-cli % npm unlink

Adjusting Directory Structure of CLI Projects

Now let us adjust the directory structure of the CLI project. Generally speaking, a CLI project looks like the following. The entry file will be under the bin folder. In the lib folder, we will put our own modules.

hello-cli % tree
├── bin
│   └── cli.js
├── lib
│   └── lib.js
├── package-lock.json
└── package.json

In package.json, adjust the path of the hello command.

{
  "name": "hello-cli",
  "version": "1.0.0",
  "description": "",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "bin": {
    "hello": "bin/cli.js"
  }
}

Add a file named lib/lib.js, and past the following code:

exports.sayHello = function (to) {
  console.log(`Hello ${to}`);
}

Move index.js to bin/cli.js, and change it’s content to the following code.

#!/usr/bin/env node

const [,, ... args] = process.argv;

const sayHello = require('../lib/lib').sayHello;
sayHello(args);

Publishing to NPM

Finally, with the following command, you can publish the hello-cli project to NPM Repository. The following –access=public refers to publishing to the public Repository. After publishing it, anyone can download and install your project. If you want to publish to a private repository, you have to pay.

% npm publish --access=public

Conclusion

After creating a Node.js project, we can feel that Node.js provides us with a fast development approach. And this approach allows you to develop Web applications (such as React/Angular/Vue.js), CLI applications, and Server side applications. This diversity is that other development environments cannot provide.