<style>
   span {cursor: pointer; color: white;}
  .span1 {background: red}
  .span2 {background: green}
  .span3 {background: blue}
</style>

<div id="div">
<span class="span1">click</span>
<span class="span2">click</span>
<span class="span3">click</span>
</div>

<script>
window.onload = function () {
  var div = document.getElementById('div');
  div.onclick = function (e) {
    e = e || event;
    var target = e.target || e.srcElement;
    if (target.parentNode == this) {
      if (target.className == 'span1') {
        alert(1);
      } else 
      if (target.className == 'span2') {
        alert(2);
      } else 
      if (target.className == 'span3') {
        alert(3);
      }
    }
  }
}
</script>