https://github.com/reggi/lerna-tutorial
:dragon: A basic description of how to use Lerna
https://github.com/reggi/lerna-tutorial
lerna monorepos tutorial
Last synced: 6 months ago
JSON representation
:dragon: A basic description of how to use Lerna
- Host: GitHub
- URL: https://github.com/reggi/lerna-tutorial
- Owner: reggi
- Created: 2016-06-21T01:29:53.000Z (over 9 years ago)
- Default Branch: master
- Last Pushed: 2019-03-12T20:23:39.000Z (over 6 years ago)
- Last Synced: 2025-04-02T11:50:05.282Z (6 months ago)
- Topics: lerna, monorepos, tutorial
- Language: JavaScript
- Homepage:
- Size: 12.7 KB
- Stars: 291
- Watchers: 5
- Forks: 41
- Open Issues: 2
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
# Lerna tutorial
## TLDR;
* `npm install` (installs lerna)
* `lerna bootstrap` (connects all the packages)
* `npm -C ./packages/usage run start` (console logs "alpha" and "beta" from combind use example module)
* Tree Structure
* `packages`
* `alpha` (`deps: []`)
* `beta` (`deps: []`)
* `usage` (`deps: ["alpha", "beta"]`)
## Summary
First off, What is [`lerna`](https://github.com/lerna/lerna)? [`lerna`](https://github.com/lerna/lerna) is a tool that allows you to maintain multiple `npm` packages within one repository.
There's a couple of benefits to this kind of approach, the paradigm is called a `monorepo`, and more can be read about it from the [source of `babel`, and `react`](https://github.com/babel/babel/blob/master/doc/design/monorepo.md).
Here's the gist:
* Single lint, build, test and release process.
* Easy to coordinate changes across modules.
* Single place to report issues.
* Easier to setup a development environment.
* Tests across modules are ran together which finds bugs that touch multiple modules easier.
## Getting started.
For this demo I'm going to be using `lerna@2.0.0-beta.20`. [`lerna`](https://github.com/lerna/lerna) is a CLI (command line interface) tool. You're going to want to install it with the `--global` (`-g`) flag.
```
npm i lerna@2.0.0-beta.20 -g
```
Then once it's done installing your going to want to run the following
```
mkdir my-monorepo && cd $_ && lerna init
```
This will do a couple of things.
* Creating packages folder.
* Updating package.json.
* Creating lerna.json.
The `/packages` folder is where all of your packages belong. Let's go about making a new package `alpha`.
```
cd packages
mkdir alpha
cd alpha
npm init -y
echo "module.exports = 'alpha'" > index.js
```
Lets go through the same steps for another package `beta`.
First go up one directory:
```
cd ..
```
Now go about creating `beta`.
```
mkdir beta
cd beta
npm init -y
echo "module.exports = 'beta'" > index.js
```
Now we're going to create a `usage` package that uses both `alpha` and `beta` as dependencies.
First go up one directory:
```
cd ..
```
Now go about creating `\usage`.
```
mkdir usage
cd usage
npm init -y
touch index.js
```
Open up `/packages/usage/index.js` in a text editor and paste this in.
```js
var alpha = require('alpha')
var beta = require('beta')
console.log(alpha + " " + beta)
```
We're almost there. At this point your whole project should look something like this:
```
.
├── README.md
├── lerna.json
├── package.json
└── packages
├── alpha
│ ├── index.js
│ └── package.json
├── beta
│ ├── index.js
│ └── package.json
└── usage
├── index.js
└── package.json
```
What you want to do now is go into `/packages/usage/package.json` and add these lines under `dependencies`.
```json
{
"dependencies": {
"alpha": "1.0.0",
"beta": "1.0.0"
}
}
```
Now you need to wire everything up with this command.
```
lerna bootstrap
```
The output from this command should look something like this:
```
Lerna v2.0.0-beta.20
Linking all dependencies
Successfully bootstrapped 3 packages.
```
Now using the `tree` command once more (`brew install tree`) we can see the folder structure we can see what [`lerna`](https://github.com/lerna/lerna) did.
```
.
├── README.md
├── lerna.json
├── package.json
└── packages
├── alpha
│ ├── index.js
│ ├── node_modules
│ └── package.json
├── beta
│ ├── index.js
│ ├── node_modules
│ └── package.json
└── usage
├── index.js
├── node_modules
│ ├── alpha
│ │ ├── index.js
│ │ └── package.json
│ └── beta
│ ├── index.js
│ └── package.json
└── package.json
```
It added two `stubbed` (my term not [`lerna`](https://github.com/lerna/lerna)'s) modules. If you peak inside `/packages/usage/node_modules/alpha/index.js` you can see what I mean.
> contents of `./packages/usage/node_modules/alpha/index.js`
```js
module.exports = require("/Users/thomas/Desktop/lerna-tutorial/packages/alpha");
```
> Note: This is an absolute path to the module. So if you ever move your lerna project you'll need to rerun `lerna bootstrap`.
And voila! When we run `node ./packages/usage/index.js` we get our expected output!
```
alpha beta
```