Yarn, like NPM, is a package manager to manage your front-end packages. When creating a Phoenix project you can't specify whether to use NPM or Yarn. And it doesn't look like there's any plan to support this; see github comment.
Prior to NPM 6, Yarn had a richer feature set and was more performant. But with the update, it looks like NPM has caught up with Yarn. So why switch?
If you're just starting out, NPM is a great choice. But if you're used to Yarn or want to explore a new package manager, then here's a quick tutorial on adding it to your Phoenix application.
I installed Yarn on my Mac with Homebrew. For further installation instructions see the Yarn docs.
$ brew install yarn
Navigate to the assets folder in your Phoenix app.
yarn init you will be prompted for information on various items. The only prompt I filled out was for the entry point.
question entry point (index.js): app.js
You can open up
package.json and see the results of
yarn init. Feel free to edit these at a later time.
yarn command to generate a
I recommend removing the
package-lock.json file since Yarn won't be using it.
That's it! You should now be ready to use Yarn to manage your front-end packages.