# How a Software Development Company Create and Publish an NPM Package
NPM is the bedrock of modern JavaScript development, a vast ecosystem of reusable code modules. For a software development company, it's more than just a tool; it's a strategic asset. By crafting and sharing their own NPM packages, companies can accelerate development, foster code reusability, and establish a unique brand identity. This empowers development teams to optimize workflow and deliver exceptional custom software development solutions.
This blog explains the steps to create and publish Node packages. Let’s get started!
## What are NPM packages?
An NPM package is a collection of JavaScript code published to the NPM registry. Packages serve as modular units for code reuse and distribution. They encapsulate functionalities, libraries, or tools.
The package.json file is a manifest for an NPM package. It resides at the root of a package directory and contains metadata about the package. Key fields include:
- **name:** Package name, unique on the NPM registry.
- **version:** Package version adhering to Semantic Versioning (SemVer).
- **description:** Brief package description.
- **main:** Entry point for the package.
- **keywords:** Keywords for discoverability.
- **author:** Package author information.
- **license:** Package license.
- **dependencies:** External dependencies required by the package.
- **devDependencies:** Development dependencies for testing and building.

Semantic Versioning mandates a version format of “MAJOR.MINOR.PATCH”. ‘MAJOR’ signifies incompatible API changes, and ‘MINOR’ adds functionality without breaking changes. Lastly, ‘PATCH’ fixes bugs without affecting existing functionality. This system ensures predictable version updates and dependency management.
## How a software development company builds NPM packages
create an NPM Package
### Setting up the NPM package
To initiate package creation, establish a new project directory. Subsequently, execute the following command within the terminal:

npm init

This command scaffolds a package.json file, which serves as the package manifest. The package.json file contains essential metadata about the package.
Essential fields in package.json
- **name:** A unique identifier for the package within the NPM registry.
- **version:** Adheres to Semantic Versioning (SemVer) for consistent version management.
- **description:** A concise explanation of the package's purpose.
- **main:** Specifies the entry point for the package, often index.js.
- **keywords:** Relevant keywords for discoverability on the NPM registry.
- **author:** Information about the package author.
- **license:** Underlines the license that allows the package distribution.

Here’s an example of package.json structure:

{
  "name": "my-package",
  "version": "1.0.0",
  "description": "A brief description of my package",
  "main": "index.js",
  "keywords": ["keyword1", "keyword2"],
  "author": "Author Name <[e-mail]>",
  "license": "MIT"
}

Optional fields in package.json
- **dependencies:** Lists production dependencies required by the package.
- **devDependencies:** Lists development dependencies used for testing, building, or tooling.
- **scripts:** Defines custom commands that can be executed using npm run.
Below is an example with dependencies and scripts by a software development company:

{
  // ... other fields
  "dependencies": {
    "lodash": "^4.17.21"
  },
  "devDependencies": {
    "jest": "^27.5.1"
  },
  "scripts": {
    "test": "jest"
  }
}

The dependencies field specifies lodash as a production dependency, while devDependencies lists jest for testing purposes. The scripts field defines a test command that executes Jest.
### Write the package code
Effective code organization is paramount for maintainable NPM packages. Modularization enhances code reusability, testability, and scalability.
**Code structure:** A common structure involves creating subdirectories to categorize code:
- src: Contains the primary package code.
- lib: Houses reusable utility functions or modules.
- test: Contains test files.
- bin: Includes executable scripts (optional).

Below is an example directory structure:
my-package

── package.json
├── src
│   ├── index.js
│   ├── module1.js
│   └── module2.js
├── lib
│   ├── util.js
├── test
│   ├── index.test.js
├── bin
│   └── my-script

Modularity and code organization: Modularity involves breaking down code into smaller, independent units. A software development company can leverage the following benefits:
- **Reusability:** Functions or components can be shared across different parts of the package or even in other projects.
- **Maintainability:** Isolating code simplifies debugging and updates.
- **Testability:** Smaller units of code are easier to test in isolation.
- **Scalability:** Modular codebases are adaptable to growing project needs.

Below is an example:

// lib/util.js
export function capitalize(str) {
  return str.charAt(0).toUpperCase() + str.slice(1);
}

// src/index.js
import { capitalize } from './lib/util';

export function greet(name) {
  return `Hello, ${capitalize(name)}!`;
}

**Package types:** The structure and content of a package depend on its purpose. Common package types include:
Utility function libraries: Provide reusable functions for common tasks.
- **Component libraries:** Offer pre-built UI components.
- **Command-line tools:** Executable scripts for performing specific actions.
- **Application frameworks:** Offer a foundation to build applications.

Below is an example:

- **Utility function library:** lodash, ramda
- **Component library:** react-bootstrap, material-ui
- **Command-line tool:** create-react-app, webpack
- **Application framework:** express, next.js

Developers create well-structured, maintainable, and reusable NPM packages by adhering to these principles.
## Testing the created NPM package
Thorough testing is crucial for ensuring package quality and reliability. It validates package functionality, prevents regressions, and increases user confidence. A software development company can leverage various frameworks and testing methods for it.
Testing frameworks: Numerous testing frameworks facilitate efficient package testing. Some of the popular packages are as follows:
- Jest: A widely-used, zero-configuration framework providing rich features for unit, integration, and snapshot testing.
- Mocha: A flexible framework allowing customization and integration with various assertion libraries.
- Jasmine: A behavior-driven development (BDD) framework emphasizing test readability.
- Unit testing: It isolates individual code units (functions, classes) to verify their correct behavior. Thus, it also ensures that each component functions as expected under various conditions.

Below is an example using Jest:
// src/myModule.js
function add(a, b) {
  return a + b;
}

export default add;

// test/myModule.test.js
import add from '../src/myModule';

test('adds two numbers', () => {
  expect(add(1, 2)).toBe(3);
});

**Integration testing:** It verifies how different code components interact. Thus, it simulates real-world scenarios and uncovers issues arising from component collaboration.
Here’s an example using Jest:

// Assuming a hypothetical `database` module
import database from './database';
import add from '../src/myModule';

test('adds numbers and stores the result in the database', async () => {
  const result = await add(1, 2);
  await database.saveResult(result);
  const retrievedResult = await database.getResult();
  expect(retrievedResult).toBe(3);
});

## How a software development company publishes NPM packages
Publishing a package in the NPM registry is necessary to distribute it to the public. Here’s how developers can update and publish the NPM package:
### Creating an NPM account
An NPM account is required to publish packages. Registration on the NPM website is straightforward.
### The npm login command
The npm login command establishes an authenticated session with the NPM registry. Upon execution, the command prompts for username, password, and email associated with the NPM account. Successful authentication grants publishing permissions.
### The npm publish command
The npm publish command uploads the package to the NPM registry. Essential options include:
- --access public: Makes the package publicly accessible (default).
- --access restricted: Restricts package visibility to specific users or organizations.

Below is an example:

npm publish --access public

Additional options for npm publish include:
- --tag: Assigns a specific tag to the published version.
- --dry-run: Performs a dry run without actually publishing.
- --otp: Requires a one-time password for added security.

### Scoped packages and private packages
Scoped packages are organized under a namespace, typically a username or organization. They are created using the @scope/package-name format.
Below is an example:

npm init --scope=@my-scope

Private packages are accessible only to specific users or organizations. They are created by default when using scopes but can also be configured for unscoped packages.
Here’s an example:

npm publish --access restricted

Developers can effectively publish their packages to the NPM registry by understanding these concepts and commands. This will help them control visibility and access according to their requirements.

## Conclusion
This was all about creating and publishing an NPM package. It includes an efficient understanding of package structure, testing, and deployment nuances. Thus, it empowers any [top software development company](https://www.unifiedinfotech.net/services/custom-software-development/) regarding code reusability and enhanced collaboration.