dom 的添加或事件绑定

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
    <title>test-del</title>
    <style>
        p{ width:400px; margin:0 auto; }
        ins{ cursor:pointer; text-decoration:none; padding-left:20px; }
    </style>
</head>
<body>
<div>
<div >
    <p><span>1</span>
        <ins>delete</ins>
    </p>
    <p><span>2</span>
        <ins>delete</ins>
    </p>
    <p><span>3</span>
        <ins>delete</ins>
    </p>
    <p><span>4</span>
        <ins>delete</ins>
    </p>
    <p><span>5</span>
        <ins>delete</ins>
    </p>
    <p><span>6</span>
        <ins>delete</ins>
    </p>
</div>
</div>
<p><a >Add</a></p>
</body>
</html>
<script type="text/javascript">
    // get elem
    function id(){
        return document.getElementById(arguments[0]);
    }
    (function(){
        var add = id('add'),
            list = id('list'),
            p = list.getElementsByTagName('p'),
            pLen = p.length,
            newLen = 0,
            newP = null,
            span;
        add.onclick = function(){
            newLen = list.getElementsByTagName('p').length + 1;
            span = '<span>' + newLen + '</span><ins>delete</ins>';
            newP = document.createElement('p');
            newP.innerHTML = span;
            newP.onclick = function(e){
                del(this, e);
            }
            list.appendChild(newP);
        }
        // del
        function del(node, e){
            e = e || window.event;
            var target = e.target || e.currentTarget,
                span = list.getElementsByTagName('span');
            if(target.tagName.toLowerCase() == 'ins'){
                node.parentNode.removeChild(node);
                // reset span number
                for(var i = 0; i < list.getElementsByTagName('p').length; i++){
                    span[i].innerHTML = i + 1;
                }
            }
        }
        // old del
        for(var i = 0; i < pLen; i++){
            p[i].onclick = function(e){
                del(this, e);
            }
        }
    }());
</script>