Understanding the Use of npm ci for Dependancy Installation

In the world of JavaScript and Node.js, managing dependencies in your projects can be crucial. One method for ensuring your dependencies are installed at the exact versions listed in your package-lock.json file is by using the command npm ci.

What is npm ci?

In npm, npm ci is a command provided by the node package manager that stands for "clean install". It offers a more reliable and faster way of installation, especially in continuous integration environments. It uses the package-lock.json file to install the exact dependencies specified, adhering strictly to the specifications made, ensuring reproducibility and consistency across installations.

Why npm ci over npm install?

Unlike the command npm install, npm ci does not modify the package-lock.json nor the node_modules directory but instead, it entirely deletes the existing node_modules and recreates it. This provides a key advantage since the exact state of dependencies is ensured, reducing bugs due to slight variations in package versions.

If there is a mismatch between package.json and package-lock.json, npm ci will result in an error, making sure the integrity of your dependencies.

Practical Applications of npm ci

Consider a scenario where you are deploying a Node.js application in a production environment or a continuous integration (CI) environment. You need to ensure that the dependencies installed match the exact versions specified in your package-lock.json file. Use npm ci like this:

npm ci

This command will read your package-lock.json, remove the existing node_modules directory, and install the exact versions of dependencies defined in the package-lock.json. Ensuring consistency and minimizing bugs in the production environment.

Best Practices and Additional Insights

When you want to add a new dependency to your project, you should use npm install. It updates both your package.json and package-lock.json with the new package information.

However, when installing dependencies for an existing project, especially in production or as part of a CI/CD pipeline, using npm ci is often the better choice for the reasons stated above. It ensures that anyone who interacts with the project will be interacting with the same set of dependencies, which further guarantees the consistency and reproducibility of your project.

In conclusion, understanding the tools and commands available in npm like npm ci is crucial to manage your dependencies effectively and maintain the integrity of your projects.