js 实现insertAfter

function insertAfter(ele,html){
    var new_ele = document.createElement("div");
    new_ele.innerHTML = html;
    var parent = ele.parentNode || document.body;
    parent.insertBefore(new_ele.firstChild, ele.nextSibling);
}

var d = document.getElementById("test");
insertAfter(d,"<div>dddddddd</div>")

var d = document.getElementById("test");
d.childNodes;//...
d.previousSibling;//null
d.nextSibling;//null
d.parentNode;//body
d.firstChild;//a
d.lastChild;//b
d.lastChild.textContent;//b
d.lastChild.previousSibling.innerHTML;//Item4