How to listen to trait value change directly from block add

I'm passing following JSON to editor.BlockManager.add() function to define my block, load it's content from the server and populate select-type trait named defaultCategory in the same manner. Everything works nice. Now I need to listen to onchange event of that select and execute some JS there. I've consulted https://grapesjs.com/docs/modules/Traits.html#add-traits-to-components but can't fugure out how to do this. Would you mind to quickly show how would I execute alert('test') when value of my trait is changed (by user selecting one of the options)? Thanks in advance. For the button there i...