Untitled

  <div class="d1" onclick="asa(this)">1

    <div class="d2" onclick="asa(this)">2

      <div class="d3" onclick="asa(this)">3</div>

    </div>

  </div>

  .d1{

    background-color:green;

    width: 150px;

    height: 150px;

    position: relative;

  }

  .d2{

    background-color:blue;

    width: 100px;

    height: 100px;

    position: absolute;

  }

  .d3{

    background-color:red;

    width: 50px;

    height: 50px;

  }

function asa(elem){

    elem.style.backgroundColor = 'yellow';

    alert(elem.className)

    elem.style.backgroundColor = '';

  }