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Building your first interactive Node JS CLI

NodeJS can be very useful when it comes to building Command-line Interfaces also known as CLI’s.

In this post, I’ll teach you how to build a CLI that asks some questions and creates a file, based on the answers.

Getting started

Let’s start by creating a brand new npm package

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

What these packages do:

  • chalk - Terminal string styling done right
  • figlet - Figlet is 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

index.js file

Now create a 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");

Planning 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.

It should ask a couple of questions and after that, show a success message with the created file path.

The questions are: what is the filename and what is the extension.

// 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 f*cking JS", {
        font: "Ghost",
        horizontalLayout: "default",
        verticalLayout: "default"
      })
    )
  );
};

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

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

run();

Now it’s time to write a function that asks 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 is to 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, 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.

d42ns41x32i4bbkjwhyw

Yay! And here is the final code:

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 f*cking JS", {
        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();

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"
  }
}
$ npm link
$ creator

Hope it helps :)