Creating a new major mode

Major modes in Emacs are really easy to create, since they are essentially just one Elisp file containing your customizations to an existing mode. The only blocker that I experienced was finding out how to get my major mode into Doom Emacs.

The first step to creating a major mode is of course, to write it. I created a directory to serve as my repository and wrote avalonia-xaml-mode.el.

1
2
3
4
5
6
7
8

(define-derived-mode avalonia-xaml-mode
  nxml-mode
  "Avalonia XAML"
  "Major mode for editing Avalonia XAML.")

(add-to-list 'auto-mode-alist '("\\.axaml\\'" . avalonia-xaml-mode))

(provide 'avalonia-xaml-mode)

define-derived-mode creates a new mode called avalonia-xaml-mode, basing the mode from Emacs’ existing nxml-mode to provide syntax highlighting. The two string arguments are just the text to display on the mode line and the docstring of the mode.

Next, we call add-to-list to associate the .axaml file extension with the mode.
Finally, we provide the mode itself.
After writing the code, we need to upload it to a Git repository. The Git repo must be named with the same name as the file containing the mode, so I named the repo avalonia-xaml-mode. Afterwards, I pushed the repository to the remote with the branch master, since this is the branch most Emacs package managers use by default when getting packages from Git repos.

After pushing the changes to the remote, I can now install it in Doom Emacs by writing the following in packages.el

1
2
3

(package! avalonia-xaml-mode
  :recipe (:host codeberg
           :repo "jhgalino/avalonia-xaml-mode"))

ReadableStream

1
2
3

const response = await fetch('example.com')
const reader = response.body.getReader()
const { value, done } = reader.read()

The ReadableStream interface is used when you want to read a stream. In our example, the body property of a Response returns a ReadableStream To use it, you must first get a reader from the ReadableStream instance. This is done by calling ReadableStream.getReader(), which returns a reader of the ReadableStream. Once you have a reader from a ReadableStream, only that reader can read from the ReadableStream. Then you must call the read method of the reader to get a value of the form { value: chunk, done: boolean }. The value is the chunk read by the reader. done represents whether the stream has been closed or not. Thus, to read all the chunks of a stream, you can use a while loop until done is set to true. Since ReadableStream is an async iterator, you can also use a for await...of loop to process each chunk.