This content originally appeared on DEV Community and was authored by Ayako yk
Understanding package.json in Node.js is crucial because it acts as the configuration file for a project. It defines how the application runs, interacts with dependencies, and provides metadata about the project.
According to Nodesource,
This file is used as a manifest, storing information about applications, modules, packages, and more.
Nodesource
Some examples of metadata in package.json include:
name: The name of the project.
"name": "my-project"
main: The entry point to the module.
"main": "app.js"
version: The version of your app or package.
"version": "1.0.0"
scripts: Custom commands like start, test, and build.
"scripts": {
"start": "node app.js",
"test": "standard"
}
dependencies / devDependencies: Lists of packages your app depends on.
"dependencies": {
"express": "^4.18.2"
}
type: Defines the module format.
"type": "module"
Module Systems
When writing a Node.js project, choosing a module system affects how you write and organize your code. If you plan to share it, it also affects how others might use it.
Two Types of Modules
A module is a self-contained block of code that can be imported and exported, allowing it to be organized, reused, and well-maintained.
Node.js provides two types of module systems:
CommonJS Modules (CJS)
This is the default module system in Node.js. It uses require() and module.exports, and is widely used throughout the Node.js ecosystem. Modules are loaded synchronously.
ES Modules (ESM)
ES Modules, or ECMAScript modules, are the modern standard for JavaScript modules. They use import and export. Modules are loaded asynchronously, which can improve performance. Since ESM is not the default in Node.js, you must explicitly declare "type": "module" in your package.json.
Publishing a Package
Node.js is an open-source runtime with a large community. The npm registry is where developers share reusable modules and packages. If you plan to contribute your module to the registry, it's important to follow best practices recommended by the Node.js community. One important guideline is to avoid the dual package hazard --- which means you should avoid mixing CommonJS (CJS) and ES Modules (ESM) in the same package.
Whether you're building a personal Node.js app or reusable library, understanding package.json and choosing the right module system will help you write clean, well-structured code.
This content originally appeared on DEV Community and was authored by Ayako yk
Ayako yk | Sciencx (2025-07-06T22:07:48+00:00) Understanding package.json and Module Types in Node.js. Retrieved from https://www.scien.cx/2025/07/06/understanding-package-json-and-module-types-in-node-js/
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