JAVASCRIPT

stimulus params

<div data-controller="item spinner">
  <button data-action="item#upvote spinner#start" 
    data-item-id-param="12345" 
    data-item-url-param="/votes"
    data-item-payload-param='{"value":"1234567"}' 
    data-item-active-param="true">…</button>
</div>

stimulus params

// ItemController
upvote(event) {
  // { id: 12345, url: "/votes", active: true, payload: { value: 1234567 } }
  console.log(event.params) 
}

// SpinnerController
start(event) {
  // {}
  console.log(event.params) 
}