How to Create Your Own npm Library 관련

How to Create an npm Library

---

In the world of JavaScript development, npm (Node Package Manager) has become an essential tool for managing dependencies and sharing reusable code. Whether you're building a simple website or a complex web application, npm libraries help streamline ...

• Setting Up a New Package
  • Step 1: Create a New Project Folder
  • Step 2: Initialize npm
• Writing Modular and Reusable Code
  • Step 3: Create an index.js File
• Adding Dependencies and Peer Dependencies
  • Step 4: Link the Package Locally

---

How to Create an npm Library

In the world of JavaScript development, npm (Node Package Manager) has become an essential tool for managing dependencies and sharing reusable code. Whether you're building a simple website or a complex web application, npm libraries help streamline ...

Creating your own npm library is a great way to share reusable code, contribute to the open-source community, or even streamline development across multiple projects. In this section, we’ll walk through the step-by-step process of setting up, coding, and preparing a library for publishing on npm.

---

Setting Up a New Package

Before writing code, you need to set up an npm package. Follow these steps:

Step 1: Create a New Project Folder

mkdir my-awesome-library
cd my-awesome-library

Step 2: Initialize npm

Run the following command to create a package.json file:

npm init

You will be prompted to enter details such as:

• Package name
• Version
• Description
• Entry point (default: index.js)
• Author
• License

💡 To skip the prompts and create a default package.json, use:

npm init -y

---

Writing Modular and Reusable Code

Now, let’s create a simple utility library that provides a function to format dates.

Step 3: Create an index.js File

Inside the project folder, create a file named index.js and add the following code:

function formatDate(date) {
  if (!(date instanceof Date)) {
    throw new Error("Invalid date");
  }
  return date.toISOString().split("T")[0];
}

module.exports = { formatDate };

---

Adding Dependencies and Peer Dependencies

Your library might depend on external packages. For example, let’s use date-fns for better date formatting.

To install it as a dependency, run:

npm install date-fns

Then, modify index.js to use date-fns:

const { format } = require("date-fns");

function formatDate(date) {
  if (!(date instanceof Date)) {
    throw new Error("Invalid date");
  }
  return format(date, "yyyy-MM-dd");
}

module.exports = { formatDate };

If you're creating a React-specific library, you should add React as a peer dependency:

npm install react --save-peer

This ensures users of your library install React separately, preventing version conflicts.

Before publishing, you should test how your package works when installed as a dependency.

Step 4: Link the Package Locally

Run the following command in your package folder:

npm link

Then, in another project where you want to use your package, navigate to that project and run:

npm link my-awesome-library

Now, you can import and use your function:

const { formatDate } = require("my-awesome-library");

console.log(formatDate(new Date())); // Output: 2025-02-04 (or the current date)

Once you're happy with your package, it's time to publish it on npm.