Managing Dependencies in Legacy Front-end Projects: A Practical Guide to Cleaning Up a Messy package.json

Marcello Gallante — Sun, 12 Jul 2026 01:40:00 +0000

A practical walkthrough of auditing, updating, and replacing dependencies using Yarn.

Front-end projects rarely become hard to maintain overnight. Instead, complexity builds gradually as dependencies accumulate, decisions age, and patterns evolve. At some point, you realize the application still works, but every change carries hidden risk. This article is a practical guide based on a real experience maintaining a legacy project that had passed through multiple developers and, over time, became difficult to manage due to inconsistent dependencies, weak documentation, and lack of technical ownership.

Is this really necessary?

Before anything else, it is worth understanding the main reasons to care about keeping your project’s dependencies up to date.

Accumulated technical risk Outdated libraries may contain security vulnerabilities, performance issues, or bugs that have already been fixed in newer versions. As updates are postponed, these risks accumulate and become harder to control.
Increasing maintenance cost The longer a dependency remains outdated, the harder it becomes to upgrade it. Large version gaps often require significant refactoring and may lock the project into obsolete solutions.
Ecosystem evolution Libraries that were once standard can lose community support, become deprecated, or be replaced by more modern alternatives. Continuing to rely on them increases technical debt and reduces long-term flexibility.
Impact on productivity Lack of clarity about what a dependency does, whether it is safe to update, or how it integrates with the rest of the system makes even simple changes slower and riskier.

Where It All Started

The trigger was a simple task: updating a specific library, Material UI.

Up to that point, I had not paid much attention to the overall state of the project’s dependencies. But when I opened the well-known package.json file, it became clear that this would not be an isolated task. It felt like a file covered in dust: dozens of dependencies, some unfamiliar, others likely outdated, and no clear understanding of what was still necessary.

That was the moment my perspective changed. This was no longer about updating a single library. It was about understanding and reorganizing the entire dependency ecosystem.

Understand before acting

Instead of updating everything blindly, I started with a structured investigation. For each dependency, I tried to answer:

What problem does it solve
Where is it used
Does it still make sense to keep it
Are there better or more modern alternatives

This last point is often overlooked. In many cases, updating is not the best decision. Replacing a dependency can lead to better long-term results, especially when the original library is no longer actively maintained.

An important point to keep in mind

Not all dependencies are direct. Many libraries bring transitive dependencies, increasing complexity without being immediately visible
There is a distinction between dependencies and devDependencies, each impacting different parts of the application lifecycle
Updating one dependency can affect others in a chain

Ignoring these aspects can easily lead to hard-to-debug issues.

Semantic Versioning in Practice

This process also pushed me to better understand semantic versioning. In practice, version numbers represent risk:

Major updates should be treated as controlled migrations
Minor updates may introduce behavioral changes
Patch updates are usually safe, but still require validation

Prefix ranges like ^ and ~ also define how flexible your project is when resolving updates, directly affecting predictability.

Yarn Commands You Should Know

Since the project used Yarn, I explored its features in more depth. Here are some commands that I found particularly useful:

yarn outdated

👆 Shows which dependencies are outdated and how far behind they are.

yarn upgrade-interactive

👆 Allows selective updates through an interactive interface.

yarn upgrade-interactive --latest

👆 Forces updates to the latest versions, ignoring version constraints.

yarn upgrade <package>

👆 Updates a specific dependency.

yarn add <package>@latest

👆 Installs the latest version explicitly.

yarn remove <package>

👆 Removes unused dependencies.

yarn audit

👆 Identifies known vulnerabilities.

Another key practice was avoiding large batch updates. Updating multiple critical dependencies at once makes it much harder to identify the source of issues.

A note on Docker environments

If your project uses Docker, there is an additional layer to consider. Updating dependencies locally does not guarantee that your container environment is up to date. Base images may also contain outdated dependencies. In these cases, it is important to:

Review the Dockerfile
Update the base image when needed
Rebuild the container after changes

What I learned from this

What started as a simple task became an important lesson. A few takeaways:

Dependency management must be continuous
Accumulated updates increase risk exponentially
Understanding comes before updating
Removing dependencies is as important as adding them

More importantly, maintaining a legacy project requires a mindset shift. It is not just about building new features, but about keeping the foundation sustainable.

Conclusion

Legacy projects are not the problem. The real issue is the lack of structured maintenance over time. Managing dependencies is one of the most effective ways to reduce risk, improve code quality, and enable long-term evolution.

If you are dealing with a similar situation, the advice is simple: do not start by updating everything. Start by understanding what you have.

DEV Community: Marcello Gallante