npm i vs npm ci: Understanding the Difference

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Introduction:

In the world of JavaScript development, npm (Node Package Manager) is an indispensable tool for managing dependencies. Whether you're a seasoned developer or just starting out, understanding the nuances between npm commands is crucial for efficient project management. Two commonly used commands, npm i and npm ci, serve similar purposes but operate differently under the hood. In this blog post, we'll delve into the differences between npm i and npm ci to help you make informed decisions when managing your projects' dependencies.

What is npm i?

The npm i command, short for npm install, is likely the most familiar and frequently used command for installing dependencies in a Node.js project. When you run npm i, npm fetches and installs all the dependencies listed in the project's package.json file, including their transitive dependencies, and stores them in the node_modules directory.

For example:

npm install

What is npm ci?

npm ci stands for npm clean install. It was introduced as a more efficient alternative to npm i for continuous integration (CI) environments, where reproducibility and speed are paramount. Unlike npm i, which may execute additional logic such as running npm scripts and saving the dependencies to package-lock.json, npm ci is designed to be deterministic and strictly adhere to the dependencies specified in the package-lock.json or npm-shrinkwrap.json file.

For example:

npm ci

Differences:

Speed: npm ci is generally faster than npm i because it skips certain steps like running lifecycle scripts and updating package-lock.json or npm-shrinkwrap.json.
Reproducibility: npm ci ensures that installations are deterministic by installing dependencies exactly as specified in the lock file. This guarantees consistent builds across different environments.
Environment: While npm i is suitable for development environments and situations where you might want to update or add dependencies, npm ci is best suited for CI/CD pipelines, production deployments, or situations where you need to ensure a clean, reproducible installation of dependencies without modification.
Side Effects: npm i can potentially have side effects such as running post-install scripts or updating lock files, whereas npm ci strictly installs dependencies without executing any scripts or altering lock files.
Use Cases: Use npm i when working on local development, adding or updating dependencies, or when you're not concerned about strict reproducibility. Reserve npm ci for automated environments like CI/CD pipelines or production deployments where you need consistent, fast, and reliable dependency installations.

Key Differences:

Feature	npm i	npm ci
Source	`package.json` (flexible)	`package-lock.json` (strict)
Behavior	Updates existing dependencies	Installs exact versions
Modifies files	May update `package-lock.json`	Does not modify files
Use case	Development (flexibility)	CI/CD, Deployment (consistency)

Choosing the Right Tool:

Use npm i during development for its flexibility in managing and experimenting with dependencies.
Use npm ci in CI/CD pipelines and deployments to ensure consistent and predictable builds and deployments across environments.

By understanding the distinctions between npm i and npm ci, you can make informed decisions, manage your dependencies effectively, and streamline your Node.js development workflow.

Conclusion:

Understanding the differences between npm i and npm ci empowers JavaScript developers to choose the appropriate command based on their specific requirements. While npm i is versatile and suitable for general development tasks, npm ci shines in environments where reproducibility and speed are critical, such as continuous integration setups and production deployments. By leveraging the right npm command for the job, developers can streamline their workflows and ensure consistent, reliable dependency management in their projects.