Build an interactive CLI with Node.js

Node.js can be very useful when it comes to building command-line interfaces (CLIs). In this post, I'll teach you how to use Node.js to build a CLI that asks some questions and creates a file based on the answers.

Get started

Let's start by creating a brand new npm package. (Npm is the JavaScript package manager.)

mkdir my-script
cd my-script
npm init

Npm will ask some questions. After that, we need to install some packages.

npm install --save chalk figlet inquirer shelljs

Here's what these packages do:

• Chalk: Terminal string styling done right
• Figlet: A program for making large letters out of ordinary text
• Inquirer: A collection of common interactive command-line user interfaces
• ShellJS: Portable Unix shell commands for Node.js

Make an index.js file

Now we'll create an index.js file with the following content:

#!/usr/bin/env node

const inquirer = require("inquirer");
const chalk = require("chalk");
const figlet = require("figlet");
const shell = require("shelljs");

Plan the CLI

It's always good to plan what a CLI needs to do before writing any code. This CLI will do just one thing: create a file.

The CLI will ask two questions—what is the filename and what is the extension?—then create the file, and show a success message with the created file path. 

// index.js

const run = async () => {
  // show script introduction
  // ask questions
  // create the file
  // show success message
};

run();

The first function is the script introduction. Let's use chalk and figlet to get the job done.

const init = () => {
  console.log(
    chalk.green(
      figlet.textSync("Node JS CLI", {
        font: "Ghost",
        horizontalLayout: "default",
        verticalLayout: "default"
      })
    )
  );
}

const run = async () => {
  // show script introduction
  init();

  // ask questions
  // create the file
  // show success message
};

run();

Second, we'll write a function that asks the questions.

const askQuestions = () => {
  const questions = [
    {
      name: "FILENAME",
      type: "input",
      message: "What is the name of the file without extension?"
    },
    {
      type: "list",
      name: "EXTENSION",
      message: "What is the file extension?",
      choices: [".rb", ".js", ".php", ".css"],
      filter: function(val) {
        return val.split(".")[1];
      }
    }
  ];
  return inquirer.prompt(questions);
};

// ...

const run = async () => {
  // show script introduction
  init();

  // ask questions
  const answers = await askQuestions();
  const { FILENAME, EXTENSION } = answers;

  // create the file
  // show success message
};

Notice the constants FILENAME and EXTENSIONS that came from inquirer.

The next step will create the file.

const createFile = (filename, extension) => {
  const filePath = `${process.cwd()}/${filename}.${extension}`
  shell.touch(filePath);
  return filePath;
};

// ...

const run = async () => {
  // show script introduction
  init();

  // ask questions
  const answers = await askQuestions();
  const { FILENAME, EXTENSION } = answers;

  // create the file
  const filePath = createFile(FILENAME, EXTENSION);

  // show success message
};

And last but not least, we'll show the success message along with the file path.

const success = (filepath) => {
  console.log(
    chalk.white.bgGreen.bold(`Done! File created at ${filepath}`)
  );
};

// ...

const run = async () => {
  // show script introduction
  init();

  // ask questions
  const answers = await askQuestions();
  const { FILENAME, EXTENSION } = answers;

  // create the file
  const filePath = createFile(FILENAME, EXTENSION);

  // show success message
  success(filePath);
};

Let's test the script by running node index.js. Here's what we get:

The full code

Here is the final code:

#!/usr/bin/env node

const inquirer = require("inquirer");
const chalk = require("chalk");
const figlet = require("figlet");
const shell = require("shelljs");

const init = () => {
  console.log(
    chalk.green(
      figlet.textSync("Node JS CLI", {
        font: "Ghost",
        horizontalLayout: "default",
        verticalLayout: "default"
      })
    )
  );
};

const askQuestions = () => {
  const questions = [
    {
      name: "FILENAME",
      type: "input",
      message: "What is the name of the file without extension?"
    },
    {
      type: "list",
      name: "EXTENSION",
      message: "What is the file extension?",
      choices: [".rb", ".js", ".php", ".css"],
      filter: function(val) {
        return val.split(".")[1];
      }
    }
  ];
  return inquirer.prompt(questions);
};

const createFile = (filename, extension) => {
  const filePath = `${process.cwd()}/${filename}.${extension}`
  shell.touch(filePath);
  return filePath;
};

const success = filepath => {
  console.log(
    chalk.white.bgGreen.bold(`Done! File created at ${filepath}`)
  );
};

const run = async () => {
  // show script introduction
  init();

  // ask questions
  const answers = await askQuestions();
  const { FILENAME, EXTENSION } = answers;

  // create the file
  const filePath = createFile(FILENAME, EXTENSION);

  // show success message
  success(filePath);
};

run();

Use the script anywhere

To execute this script anywhere, add a bin section in your package.json file and run npm link.

{
  "name": "creator",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "node index.js"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "chalk": "^2.4.1",
    "figlet": "^1.2.0",
    "inquirer": "^6.0.0",
    "shelljs": "^0.8.2"
  },
  "bin": {
    "creator": "./index.js"
  }
}

Running npm link makes this script available anywhere. 

That's what happens when you run this command:

/usr/bin/creator -> /usr/lib/node_modules/creator/index.js
/usr/lib/node_modules/creator -> /home/hugo/code/creator

It links the index.js file as an executable. This is only possible because of the first line of the CLI script: #!/usr/bin/env node.

Now we can run this script by calling:

$ creator

Wrapping up

As you can see, Node.js makes it very easy to build nice command-line tools! If you want to go even further, check this other packages:

• meow – a simple command-line helper
• yargs – a command-line opt-string parser
• pkg – package your Node.js project into an executable

Tell us about your experience building a CLI in the comments.