<div contenteditable="true" id="editable-div">
  <p id="paragraph">
    Lorem <em>ipsum</em> dolor sit <strong id="stong-el">amet</strong>
  <p>
</div>

const div = document.getElementById('editable-div');
div.addEventListener('keydown', event => { /* ??? */ }, false);

// either
const el = document.getElementById('paragraph');

// or
const el = document.getElementById('stong-el');

el.addEventListener('keydown', event => { /* ??? */ }, false);