HTML

<p id="container">
    <ul id="wrapper" class="clearfix">
        <li>0</li>
        <li>1</li>
        <li>2</li>
        <li>3</li>
        <li>4</li>
        <li>5</li>
        <li>6</li>
    </ul>
</p>

JS

<script>
    var conainer = document.getElementById("container");
    var wrapper = document.getElementById("wrapper");
    var liList = wrapper.getElementsByTagName("li");
 
    for(var i = 0, len = liList.length; i < len; i++){
        (function(m) {
            liList[m].onclick = function() {
                alert(m);
            }
        })(i);
    }
</script>