[Vlasenko Fedor]

<section class="right" id="nav">
  <div id="b1" onmouseover="test(this)">Кнопка 1</div>
  <div id="b2" onmouseover="test(this)">Кнопка 2</div>
  <div id="b3" onmouseover="test(this)">Кнопка 3</div>
  <div id="b4" onmouseover="test(this)">Кнопка 4</div>
</section>
<script>
  function test(el) {
    console.log(el.id);
  }
</script>