Quick help needed: Lovelace custom card installation

Development
1

Have a js for a custom card but Lovelace does not see it. What can be a problem?
bkk-stop-card.js:

class BKK4StopCard extends HTMLElement {
 }
  customElements.define('bkk-stop-card', BKK4StopCard);

stored here:

/config/www/bkk-stop-card.js

ui-lovelace.yaml:

resources:
  - type: js
    url: /local/bkk-stop-card.js

Card says:
image