As I progressed with my personal learning project, AutoScout, one of the important tasks was ensuring that my project would run smoothly across different environments. With the variety of Node.js versions available, I needed a way to make sure that my codebase would only run on compatible versions, and wouldn’t break in future updates.

That's when I discovered the power of the engines field in package.json.

In this post, I’ll take you through the process of configuring the engines field, the challenges I faced, and how it improved the overall stability of the AutoScout project.

Why the engines Field?

When you’re developing a project, especially one that you intend to deploy across multiple environments or share with others, it’s crucial to define which versions of tools, such as Node.js, are supported. Without this, you risk running into compatibility issues where certain parts of your codebase may break because they depend on features or syntax that are only available in specific versions of Node.js.

AutoScout, being a personal learning project with a backend powered by NestJS and TypeORM, was an ideal candidate for this approach. I knew that controlling the environment was key.

To avoid any nasty surprises when deploying to different servers or working on the project from different machines, I had to ensure the project explicitly stated which versions it was compatible with.

Step 1: Adding the engines Field

The first step was adding the engines field to the package.json file. Here's how I structured it:

"engines": {
"node": ">=20.18.1"
}
This configuration ensures that AutoScout will run on any version of Node.js that is 20.18.1 or greater. I specifically chose Node.js version 20 because it’s an LTS version, offering a stable environment for long-term development and deployment.

Step 2: Testing Compatibility

Once I added the engines field to package.json, it was time to test. This field alone doesn't enforce version checking; it simply serves as a declaration of compatibility. To take full advantage of it, I needed to ensure that npm would enforce these version constraints.

For this, I added the following configuration to my .npmrc file:

engine-strict=true
This option makes npm throw an error if the installed version of Node.js doesn’t match the version defined in the engines field of package.json. This ensures that when installing dependencies, only compatible Node.js versions are used, protecting the project from potential version conflicts.

By adding the .npmrc file with this configuration, I created an extra layer of protection, which prevented issues when installing dependencies with incompatible Node.js versions. This gave me confidence that the project would remain stable regardless of where it was run.

Step 3: Adding Version-Specific Dependencies
In addition to the engines field, I made sure that certain dependencies, which were only compatible with specific Node.js versions, were versioned appropriately.

Some libraries I was using in AutoScout had breaking changes across different versions of Node.js, so I added version constraints to ensure the correct versions were installed.

"dependencies": {
"@nestjs/common": "^10.0.0",
"bcrypt": "^5.1.1"
}
By adding these version constraints, I avoided any accidental upgrades that might introduce issues or bugs to the project.

In particular, I ensured that my core dependencies (like NestJS and bcrypt) were aligned with the correct versions for the Node.js environment, making the development process smoother and reducing the risk of unexpected errors.

Step 4: Final Thoughts

While the engines field might seem like a small addition to your package.json, it has been an essential tool for ensuring that AutoScout remains stable as I continue developing and testing it across different environments.

By locking down the version of Node.js and dependencies, I've reduced the risk of incompatibilities and can work more efficiently, knowing my environment is predictable.

Conclusion:

The engines field in package.json is a simple but powerful way to define the compatibility of your project with different versions of Node.js and other tools.
It’s been incredibly helpful in my learning journey with AutoScout, and I encourage you to take a few minutes to add it to your own projects. Whether you're building something personal or experimenting with new technologies, it's always worth ensuring that your environment is controlled and predictable.

Stay tuned for more updates on AutoScout and other development tips!