Unleashing the Power of Monorepos with Lerna — Grow Together By Sharing Knowledge

5 min readJan 25, 2024

Monorepos, short for “monolithic repositories,” has gained popularity in the software development world for managing large-scale projects efficiently. One tool that stands out in the world of monorepos is Lerna. In this blog, Let’s delve into unleashing the power of Monorepos with Lerna, how to use it, and explore its pros and cons.

1. What is Lerna?

Lerna is a tool for managing JavaScript projects with multiple packages. It optimizes the workflow around multi-package repositories with git and npm. By optimizing the workflow, Lerna makes it easier to maintain and manage large-scale projects with multiple packages or modules.

Installation:

Before diving into usage, let’s install Lerna globally using npm:

npm install -g lerna

2. Setting Up a Monorepo with Lerna

Lerna works seamlessly with a monorepo structure. Let’s set up a simple example with two packages — package-a and package-b.

Initializing Lerna:

lerna init

This command initializes a new Lerna repository, creating a packages folder and a basic configuration file.

Creating Packages:

lerna create package-a
lerna create package-b

This command creates two packages, package-a and package-b, within the packages directory.

Linking Packages:

lerna link

Lerna’s link command establishes symlinks between the packages, allowing for easy cross-package development.
Note: The "link" command was removed by default in v7, and is no longer maintained.

Installing Dependencies:

lerna bootstrap

The bootstrap command installs all dependencies and links any cross-dependencies in the monorepo.
Note: The "bootstrap" command was removed by default in v7, and is no longer maintained.

3. Lerna in Action:

Let’s explore some common Lerna commands:

lerna exec: Run a command in each package.

Result:

lerna run: Run a script in each package.

Result:

lerna add: Add a dependency to packages.

4. Pros and Cons of Lerna:

Pros:

Cons:

5. List of commands:

6. When to Use Lerna:

Large-Scale Projects: Lerna is particularly beneficial for managing large-scale projects with multiple packages or modules.
Cross-Package Development: When there is a need for efficient linking and development across packages.
Consistent Versioning: Projects that require consistent versioning across packages.

Use cases:

1. Monorepo Management:

Use Case: You have a large-scale project with multiple packages or modules that share common code and dependencies.
How Lerna Helps: Lerna simplifies the management of a monorepo, allowing you to version, test, and publish packages together or independently.

2. Cross-Package Development:

Use Case: You need to work on multiple packages simultaneously and test changes across packages during development.
How Lerna Helps: Lerna enables easy linking and testing between packages, streamlining the development process and improving collaboration.

3. Consistent Versioning:

Use Case: You want to ensure consistent versioning across all packages to maintain compatibility and manage dependencies.
How Lerna Helps: Lerna automates versioning, ensuring that all packages in the monorepo have the same version number when a release is made.

4. Dependency Management:

Use Case: Managing dependencies across multiple packages becomes challenging, especially when some packages depend on others.
How Lerna Helps: Lerna assists in managing dependencies by optimizing the installation of shared dependencies and avoiding duplication.

5. Parallelized Tasks:

Use Case: You want to speed up tasks such as running tests, building, or linting across multiple packages concurrently.
How Lerna Helps: Lerna provides concurrency options, allowing you to parallelize tasks and significantly reduce the time needed for development tasks.

6. Automated Releases:

Use Case: You need a streamlined process for versioning and publishing packages whenever changes are made.
How Lerna Helps: Lerna automates the release process, making it easier to bump versions, create Git tags, and publish updated packages.

7. Simplified Task Execution:

Use Case: Executing commands or scripts across all packages is a common requirement for tasks like linting or running tests.
How Lerna Helps: Lerna simplifies the execution of tasks across packages with commands like lerna exec and lerna run.

8. CI/CD Integration:

Use Case: You want to integrate the monorepo structure with your continuous integration/continuous deployment (CI/CD) pipeline.
How Lerna Helps: Lerna is compatible with popular CI/CD systems, allowing you to seamlessly integrate it into your automated build and deployment processes.

9. Efficient Workspace Configuration:

Use Case: You aim to structure your monorepo efficiently, providing a clear organization of packages and their dependencies.
How Lerna Helps: Lerna helps configure workspaces, allowing you to specify package locations and manage dependencies in a structured manner.

10. Task Automation and Maintenance:

Use Case: Automating routine tasks such as cleaning or repairing the monorepo is crucial for maintaining a healthy codebase.
How Lerna Helps: Lerna offers commands like lerna clean and lerna repair for automating maintenance tasks.

7. Conclusion:

In conclusion, Lerna is a powerful tool that streamlines the development workflow in monorepos. While it may have a learning curve, the benefits it brings to managing complex projects make it a valuable addition to the toolkit of any front-end engineer or team lead.

References:

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Originally published at https://techtalkbook.com on January 25, 2024.