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Mono Repo with Lerna

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Lerna is a tool for managing JavaScript projects with multiple packages. It optimizes the workflow around managing multi-package repositories with git and npm.

This article will show you how to create a mono repo with Lerna.

tip

You can checkout tutorial video below.

Create a new project​

Create a new project with the following command:

mkdir lerna-example
cd lerna-example

npm init -y

Initialize Lerna​

Initialize Lerna with the following command:

npx lerna init

This will create a lerna.json file in the root of the project.

Create a package​

Create a new package with the following command:

npx lerna create @lerna-example/package-1 -y

This will create a new folder packages/package-1 with a package.json file.

Most common commands​

Now that we have a mono repo with a package, it helps to manage all npm packages in root package.json file and node modules in root node_modules folder. So, if we npm install a package in root package.json file, it will be installed in root node_modules folder and all packages in packages folder will be able to use it.

To manage the packages, I often use the following commands:

Run certain npm script in all packages (ex: build)​

npx lerna run build

Run npm script in a certain package (ex: build in package-1)​

npx lerna --scope=@lerna-example/package-1 run build

Publish all packages​

To push mono-repository to npm which is the concept of using npm scope. Meaning it is necessary to create a organization under the account. After that, you can publish packages to npm with the following command:

npx lerna publish

The command above exectues actually npx lerna version and npx lerna publish from-packages under the hood.

You can also run it seperately.

If you are using a free tier account, you might come across the following error:

danger

? Are you sure you want to publish these packages? Yes
lerna info publish Publishing packages to npm...
lerna ERR! E402 You must sign up for private packages

The reason is npm treats all packages under the same scope as private packages. So, you either need to upgrade your account to a paid tier or you need to set access to public like below:

{
  "publishConfig": {
    "access": "public"
  }
}

Congratulations! You have successfully created a mono repo with Lerna. 🎉🎉🎉🎉🎉🎉🎉🎉🎉🎉🎉🎉🎉🎉

info

If you want to publish packages to npm, you can also checkout my another video tutorial below.