Tom Select is an improved FORK of SelectizeJS that I have been using for many years. Most notably, it does not use jQuery.

Resources:

Special thanks to secretpray for helping me with this one!

Install

console

yarn add tom-select

app/javascript/stylesheets/application.scss

@import "tom-select/dist/css/tom-select.bootstrap5";

or

@import 'tom-select/dist/css/tom-select.css';

app/controllers/tags_controller.rb

class TagsController < ApplicationController
  def create
    tag = Tag.new(tag_params)
    if tag.valid?
      tag.save
      render json: tag
    end
  end

  private

  def tag_params
    params.require(:tag).permit(:name)
  end
end

config/routes.rb

  resources :tags, only: :create

app/views/posts/_form.html.erb

  <div class="field">
    <%= form.label :tags %>
    <%= form.select :tag_ids, Tag.all.pluck(:name, :id), {}, { multiple: true, id: "select-tags" } %>
  </div>

app/views/layouts/application.html.erb

    <%= stylesheet_link_tag 'application', media: 'all', 'data-turbolinks-track': 'reload' %>
    <%= stylesheet_pack_tag 'application', media: 'all', 'data-turbolinks-track': 'reload' %>
    <%= javascript_pack_tag 'application', 'data-turbolinks-track': 'reload' %>

app/javascript/packs/application.js

require("utilities/tom_select")

The only tricky thing - creating tags. We need to POST to tags#create and get back the json result

app/javascript/utilities/tom_select.js

import 'tom-select'
import TomSelect from "tom-select"

document.addEventListener("turbolinks:load", () => {
  const selectInput = document.getElementById('select-tags')
  if (selectInput) {
    new TomSelect(selectInput, {
      plugins: {
        remove_button:{
          title:'Remove this item',
        }
      },
  		onItemAdd:function(){
  			this.setTextboxValue('');
  			this.refreshOptions();
  		},
      persist: false,
      create: function(input, callback) {
        const data = { name: input }
        const token = document.querySelector('meta[name="csrf-token"]').content
        fetch('/tags', {
          method: 'POST',
          headers:  {
            "X-CSRF-Token": token,
            "Content-Type": "application/json",
            "Accept": "application/json"
          },
          body: JSON.stringify(data)
        })
        .then((response) => {
          return response.json();
        })
        .then((data) => {
          callback({value: data.id, text: data.name })
        });
      },
      onDelete: function(values) {
        return confirm(values.length > 1 ? 'Are you sure you want to remove these ' + values.length + ' items?' : 'Are you sure you want to remove "' + values[0] + '"?');
      }
    })
  }
})

ALTERNATIVE - async/await variant for create

app/javascript/utilities/tom_select.js

      create: async function(input, callback) {
        const data = { name: input }
        const token = document.querySelector('meta[name="csrf-token"]').content
        let response = await fetch('/tags', {
          method: 'POST',
          headers:  {
            "X-CSRF-Token": token,
            "Content-Type": "application/json",
            "Accept": "application/json"
          },
          body: JSON.stringify(data)
        })
        let newTag = await response.json();

        return await callback({ value: newTag.id, text: newTag.name })
      },

ALTERNATIVE - Stimulus variant

app/views/posts/_form.html.erb

  <div class="field" data-controller="tom-select">
    <%= form.label :tags %>
    <%= form.select :tag_ids, Tag.all.pluck(:name, :id), {}, { multiple: true, id: "select-tags" } %>
  </div>

app/javascript/controllers/tom_select_controller.js

IN THIS CASE YOU CAN SKIP THE TURBOLINKS RELOAD LINE HERE!

document.addEventListener("turbolinks:load", () => {`

app/javascript/controllers/tom_select_controller.js

import { Controller } from "stimulus"

import 'tom-select'
import TomSelect from "tom-select"

export default class extends Controller {
  connect() {
    console.log('tom_select_controller connected')

    ...

    const selectInput = document.getElementById('select-tags')
    if (selectInput) {
      new TomSelect(selectInput, {

    ...

  }
}

That’s it!