<div id="selectValues">

  <select class="select" data-mdb-clear-button="true" data-mdb-container="#selectValues">

    <option value="1">One</option>

    <option value="2">Two</option>

    <option value="3">Three</option>

    <option value="4">Four</option>

    <option value="5">Five</option>

  </select>

</div>

​

const clearBtn = document.querySelector("#selectValues .select-clear-btn")

clearBtn.addEventListener('click', ()=>{

  console.log('cleared')

})

​