add js libraries to rails project with yarn

rails-yarn.md

How to add js library to Ruby on Rails project with yarn

1. Install yarn on your system. For Debian/Ubuntu Linux:

$ curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -
$ echo "deb https://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list
$ sudo apt-get update && sudo apt-get install yarn

2. To add any library, for example jquery, to Ruby on Rails 5.1 application with yarn(from npm) type in terminal:

$ yarn add jquery

This will add jquery dependency to package.json file in root directory and generate yarn.lock file(similar to Gemfile and Gemfile.lock for Ruby gems).

3. Run:

$ yarn              # like 'bundle' for ruby gems

or

$ yarn install      # like 'bundle install' for ruby gems

This will add jquery to /node_modules in the root of rails project.

4. Require jquery in application.js file:

# app/assets/javascripts/application.js
//= require js

That's it.

However! To install datatables.net:

$ yarn add datatables.net
$ yarn

To require library in application.js you must directly specify path to the library location(/node_modules/datatables.net/js/jquery.dataTables). Don't now if it's a bug or feature :)

# app/assets/javascripts/application.js
...
//= require datatables.net/js/jquery.dataTables

This location may be find at /node_modules/_modul_name/package.json - key main.

For datatables.net module it was: "main": "./js/jquery.dataTables.js"

Any hints in why its necessary to add the path for datatables but not for jquery?