And by context, I can tell that require jquery adds the jQuery libraries. But where does it get these jQuery libraries from? I don't see any jquery. I can't find these files anywhere. Rails mainly works with gems.
Gems are pieces of ruby code which you can tell to add to your rails app via bundler. So the manifest file tells rails "Hey, include these file for me, in this specific order" That is why you can include files that you wrote which are in the assets folder and files are included in a gem.
If you don't include the files in the manifest but still install the gem that is equivalent to writing a css or js file, placing it in some folder and not telling rails that it exists. When you do tell rails where it is, via the manifest file, it will include it in the asset compilation process and you can access it regularly. To understand it, you have to look at Sprockets , which is used for compiling and serving web assets.
You can find these files using gem which. Here is an example with bootstrap-sass :. It's rails magic! So no you cannot see the files within your own project directory. Also, if you really want to change something in the gem, you can fork the code into you own github, change things on your local branch, and then specify your own github as the source for the gem in your gemfile such as I think it gets them from the gem s that are installed on your system and included in this project via your Gemfile.
Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. If you want to install bootstrap for instance:. NPM stores downloaded packages in. Yarn is a more recent package manager for Javascript. It fetches packages from the NPM repository but does more than that. It allows you to lock the desired versions of your NPM packages in a yarn. In a Rails 6 application, when you need a Javascript library, you:.
Note: NPM has since added a lock feature too through package-lock. ES6 is a new Javascript standard a new version of Javascript if you will. It comes with new super-handy features such as class definition, destructuring, arrow functions, etc. Goodbye Coffeescript, I always hated you.
Babel is the compiler that does this translation. There is Babel and there is Yarn and their configuration files and there is the need to automate the compilation of your assets and the management of environments and so on. Because you want to focus on writing code and automate assets precompilation, you will be using Webpack which takes the role of bandmaster.
It takes your assets and passes each one of them to the right plugins. The plugins then make the right tool process the input file and give the expected output. For instance, Webpack can:.
Webpacker is a gem that nicely includes Webpack in your Rails application. It comes with some initial and sufficient to begin with configuration files so that you can start by writing actual code without worrying about configuration.
This article is focused on Javascript so I'm not going to say more about this, just keep in mind that it is turned off by default so you won't waste time debugging what is default behavior, not a bug. Like Webpack, Sprockets is an asset pipeline, which means it takes assets files as input Javascript, CSS, images, etc.
As of Rails 6, Webpack er replaces Sprockets as the new standard for writing Javascript in your Rails applications. However, Sprockets is still the default way of adding CSS to your applications.
With Sprockets you:. If you want to include an asset from the Sprockets pipeline, you would:. Ideally you should spend some time learning ES6 but meanwhile I can at least say this:. Webpack is different than Sprockets in the sense that it compiles modules. ES6 modules to be precise in the case of Rails 6 with a default configuration. What does that imply? Well, it implies that everything you declare in a module is kind of namespaced because it is not meant to be accessible from the global scope but rather imported then used.
Let me give you an example. These and other use cases are great reasons to use JavaScript in your application. In fact, the demand for JavaScript has been increasing. You can even use it to write your backend. At the time of writing, the latest version of the framework is Rails 6, and it has brought some changes to the way you interact with JavaScript. But starting from Rails 6, Webpacker is the default compiler for JavaScript.
You won't find your JavaScript folder in the same place as you did in Rails 5. In that folder you will find the application. It will be imported by default in the application.
If you want your JavaScript to be available in all views or pages, you can just put it in the application. The first four lines are there by default. I have added a console. But you may not always want your JavaScript code to be loaded on every page. Instead, you can make the script available only when visiting a specific page. Remember that you need to add the file in the packs directory. I hope this article helps clear up any confusion you might have when updating your app to Rails 6, or if you just got started with Rails.
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