??function?get_previousSibling(x){
????????var?x=x.previousSibling;
????????while(x&&x.nodeType!=1){
????????????x=x.previousSibling;
????????}
????????return?x
????}

????var?x=document.getElementsByTagName("li")[3];
????document.write("<br>"+"<br>"+x.nodeName);
????document.write("=")
????document.write(x.innerHTML);
????
????var?a=get_previousSibling(x)
????
????if(a!=null){
????document.write("<br?/>previoussibling:?");
????document.write(a.nodeName);
????document.write("=")
????document.write(a.innerHTML);
????}
????else{
????????document.write("<br>已經是最后一個節點");
????}

為什么這里“var x=document.getElementsByTagName("li")[3];” 寫3的時候，輸出是

“LI=css3
已經是最后一個節點”

之前的空白節點不是已經篩選過了嗎？，那應該是“html”才對啊。

難道我篩選的函數寫錯了？