How to publish a package to npm: a step-by-step guide

Publishing packages on NPM (Node package manager) is not only a way to share your work with other developers, but also to stand out in the development community. Imagine creating a reusable solution that can be integrated into various projects around the world, saving other programmers time and effort.

In this article, you will learn, step by step, how to configure, publish, and maintain your own package on NPM, making your contributions accessible and increasing your visibility as a developer.

Prerequisites

Before you start, make sure you have:

• NPM installed. You can download it from nodejs.org or use NVM (Node version manager).
• An account created on npmjs.com

Run the commands below in the terminal to verify that the installation of Node.js and NPM was successful.

node -v
npm -v

If the installation is correct, the terminal will display the version of each.
The result will be similar to the one below:

$ v20.18.0 # node -v
$ 10.8.2 # npm -v

Configuring the project

Start by creating a folder with the name you want for the package. In my case I chose "string-reverser-jm".

mkdir string-reverser-jm # cria a pasta via terminal
cd string-reverser-jm # acessa a pasta via terminal

Initialize NPM:

npm init

When executing the above command, the terminal will ask you a few questions to create the package.json file.
Below is an explanation of each item that we need to fill out.

• name: A unique identifier for the package.
• version: Use semantic versioning to indicate changes.
• description: A brief explanation of what the package does.
• main: The entry point file, for example, index.js.
• keywords: Keywords to categorize and make it easier for other developers to find the package.
• author: Add relevant author details.
• license: The license defines how the code can be used, modified and distributed by others. The most common license is the MIT, which is permissive and allows great freedom of use, as long as the original copyright notice is provided.

If you finish the questions and NPM created the file without any of this information, open the created file in an editor and add whatever is missing.

Example:

{
  "name": "string-reverser-jm",
  "version": "1.0.0",
  "description": "A simple utility to reverse strings, useful for demonstrations and small projects.",
  "main": "index.js",
  "scripts": {
    "test": "echo \"No test specified\" && exit 1"
  },
  "author": "Juliana Macedo <contact@starcoders.info> (https://www.starcoders.info)",
  "keywords": [
    "string",
    "reverse",
    "utility"
  ],
  "license": "MIT"
}

Writing the code

Create the index.js file in the root of the project.

function reverseString(str) {
  if (typeof str !== "string") {
    throw new TypeError("Expected a string as input");
  }
  return str.split("").reverse().join("");
}

module.exports = reverseString;

Testing the package

To test the package before publishing it, we will use the npm link command

In the package directory, run the command:

npm link

In the project where you want to test the package, run the command:

node -v
npm -v

Import and use the package in your test project to ensure it is working:

$ v20.18.0 # node -v
$ 10.8.2 # npm -v

To remove the created links, simply run the command npm unlink string-reverser-jm in the test project directory and then npm unlink in the package directory.

Preparing the package for publication

First, create a Git repository for the package and link it to NPM. This increases transparency and trust by making source code available, facilitates collaborations and community contributions, and enables automation with CI/CD for more efficient management and maintenance.

To link to NPM, copy the https address of the repository and add it to package.json:

mkdir string-reverser-jm # cria a pasta via terminal
cd string-reverser-jm # acessa a pasta via terminal

• .gitignore: Create a .gitignore file to exclude folders and files, such as node_modules and .env, from versioning.
• .npmignore: Create a .npmignore file to specify which files and folders should not be included in the NPM package.
• README.md: Create a file with information about the package.

Publishing the package

Log in to NPM using your login details:

npm init

Run the command below to publish the package:

{
  "name": "string-reverser-jm",
  "version": "1.0.0",
  "description": "A simple utility to reverse strings, useful for demonstrations and small projects.",
  "main": "index.js",
  "scripts": {
    "test": "echo \"No test specified\" && exit 1"
  },
  "author": "Juliana Macedo <contact@starcoders.info> (https://www.starcoders.info)",
  "keywords": [
    "string",
    "reverse",
    "utility"
  ],
  "license": "MIT"
}

Okay, the package will soon be available in the NPM registry!
https://www.npmjs.com/package/string-reverser-jm

Updating the package

When making updates or bug fixes, increase the version number in package.json according to semantic versioning using one of the commands below:

function reverseString(str) {
  if (typeof str !== "string") {
    throw new TypeError("Expected a string as input");
  }
  return str.split("").reverse().join("");
}

module.exports = reverseString;

And then publish the updated version:

npm link

Frequent problems:

• Package Name Already Taken: If publishing fails because a package with the same name already exists, choose another name, one that has not yet been taken.
• Authentication Errors: Make sure you are logged in and have all the necessary permissions to publish.
• Version Conflicts: If you try to publish without updating the version number, NPM will reject your post. Use npm version to increase the version.

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