How to extend DocumentSettings Components

[ibes]

To make it a clear example:

I would like to add a character count to the excerpt field.

In Classic Editor I would do a litte jQuery for that.
But in Gutenberg I need to get inside the React Component, right?

Is there a way to extend that components?
I heard of Higher Level Components and imagine to wrap the original compoent to extend it with further features?!

I am React beginner and hope to learn my way to have full control over the admin panel again.

[t-hamano]

Hi @ibes,

Gutenberg has pre-defineds place for developers to inject items, which can be achieved by using SlotFills.
SlotFills Reference | Block Editor Handbook | WordPress Developer Resources

For example, PluginPostStatusInfo may probably suit your purposes.
PluginPostStatusInfo | Block Editor Handbook | WordPress Developer Resources

The getEditedPostAttribute may be used to retrieve the excerpt string to count the number of characters.
gutenberg/data-core-editor.md at trunk · WordPress/gutenberg · GitHub

The following references may be helpful for basic instructions on how to create a plugin to extend the block editor.
How to use JavaScript with the Block Editor | Block Editor Handbook | WordPress Developer Resources