« Continued from - How to create a NodeJS NPM package

Adding package dependencies

Now that we created the package, let’s add some dependencies to it.

We also want the user to create a file automatically file.txt with a --new option. For this, we will have to package a default file with the package.

We will change the command line options for our program as shown below

To convert a file we pass it as a named argument with --file

uppercaseme --file file.txt

And to create a new file file.txt in the working directory

uppercaseme --new

To achieve this, we will install the commander module.

npm install commander

Note that this is a local install for commander

Modifying code to include commander

This is not a tutorial on using commander module - so we’ll look at the basic usage required in our case.

First we require("commander") in our code and then set the options like version, command line named arguments. This module then parses the arguments and gives us some usable info.


"use strict"
var fs = require('fs');
var path = require('path');

var program = require('commander');

program.version('0.1.1')
	.option('-n, --new', 'Create a test file')
	.option('--file [filename]', 'Filename to convert')
	.parse(process.argv);

Then we use the program variable to access the options

if(program.new) {
....

var myfile = program.file;

Commander also automatically generates command line help for our program when used with --help option

Updated code

Change back to our test directory and open src/lib/uppercaseme.js. Change the code to:

"use strict"
var fs = require('fs');
var path = require('path');

var program = require('commander');

/* Define configuration for commander */
program.version('0.1.1')
	.option('-n, --new', 'Create a test file')
	.option('--file [filename]', 'Filename to convert')
	.parse(process.argv);
	
function copyFile(from, to) {
	return fs.createReadStream(from).pipe(fs.createWriteStream(to));
}

function convertThis() {

	if(program.new) {
		var newfile = path.join(path.dirname(fs.realpathSync(__filename)), '../lib/examples/file.txt');
		copyFile(newfile, path.join(process.cwd(), "file.txt"));
	} else if(program.file) {
		var myfile = program.file;
		if(fs.existsSync(myfile)) {
			var content = fs.readFileSync(myfile, 'utf8');
			fs.writeFileSync(myfile, content.toUpperCase());
			console.log("Done");
		} else {
			console.log("File does not exist - " + myfile);
			console.log("OR Create a new file with the --new option");
		}
	} else {
		console.log("Pass a file name/path");
	}
}

exports.convert = convertThis;

To test this update, change back to our test directory and type

node ./src/bin/uppercaseme --new

This creates a file file.txt in our current directory with regular text. And then we can convert it to uppercase using

node ./src/bin/uppercaseme --file file.txt

Finally, let’s add these dependencies to our package.json

{
  "author": "Anup Shinde",
  "name": "uppercaseme",
  "description": "Converts files to uppercase",
  "version": "0.1.2",
  "repository": {
    "url": ""
  },
  "main": "./lib/uppercaseme",
  "keywords": [
    "upper",
    "case",
    "file"
  ],
  "bin": {
    "uppercaseme": "./bin/uppercaseme"
  },
  "dependencies": {
	"commander": "2.0.0"
  },
  "engines": {
    "node": "*"
  }
}

Here we updated our package version and added a dependency commander. The version for these dependencies from node_modules/<dependency>/package.json

We can now publish it from the src directory using

npm publish

And then we can do a global install using

npm install -g uppercaseme

We can now use our exciting new program to do one of these, preferably in some other directory

uppercaseme --help

uppercaseme --new

uppercaseme --file file.txt

NOTE on not-polluting NPM registry with examples.

While NPM makes it easier for us to distribute packages, I would recommend that you unpublished each and every version of the sample packages that you created during this tutorial

You can do so from your src directory

npm unpublish --force

NPM also maintains a local cache so that it does not download stuff everytime you do npm install. You can clean this cache using

npm cache clean

Common issues when creating NPM packages for first time:

  • NPM caching can cause “old-code” issues in testing if you are “just testing” publishing same version multiple times (in combination with install, unpublish). This is because npm installed from local cache - which is probably from your first install of that specific version.

  • If you are using Windows for development - make sure you test it on Linux/Mac environments too. Line-feed-character mismatches in your bin files may result in errors like node - command not found

If you found this useful, please share.

Happy coding!!!