<!DOCTYPE HTML>
<html lang="en-US">
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<ul>
<li>1</li>
<li>2</li>
<li><i><b>3</b></i></li>
<li>4</li>
</ul>
<script>
document.getElementsByTagName("ul")[0].onclick = function( e ) {
var target = e ? e.target : event.srcElement;
while ( target != this && target.nodeName.toLowerCase() != "li" ) {
target = target.parentNode;
}
if ( target == this ) { return; }
var index = 0;
while ( (target = target.previousSibling) ) {
if ( target.nodeType === 1 ) {
index++;
}
}
alert ( index )
};
</script>
</body>
</html>