Stimulus Rails - Count characters in input field

** Disclaimer: I’m still experimenting with Stimulus and this might not be the best way to do things **

Prerequisites:

• rails 6
• stimulus 2

Final solution demo:

HOWTO:

/app/javascript/controllers/countchar_controller.js

import { Controller } from "stimulus"
export default class extends Controller {
  static targets = [ "name", "counter" ]

  countCharacters(event) {
    let characters = this.nameTarget.value.length;
    this.counterTarget.innerText = characters;
  }
}

/app/views/posts/_form.html.erb

<div data-controller="countchar">
  <%= form.text_area :content, data: { countchar_target: 'name', action: 'keyup->countchar#countCharacters' } %>
  Characters: <span data-countchar-target='counter'><%= post.content.to_s.size %></span>
</div>