const unsigned short ELEMENT_NODE = 1;
const unsigned short ATTRIBUTE_NODE = 2;
const unsigned short TEXT_NODE = 3;
const unsigned short CDATA_SECTION_NODE = 4;
const unsigned short ENTITY_REFERENCE_NODE = 5;
const unsigned short ENTITY_NODE = 6;
const unsigned short PROCESSING_INSTRUCTION_NODE = 7;
const unsigned short COMMENT_NODE = 8;
const unsigned short DOCUMENT_NODE = 9;
const unsigned short DOCUMENT_TYPE_NODE = 10;
const unsigned short DOCUMENT_FRAGMENT_NODE = 11;
const unsigned short NOTATION_NODE = 12;

但如果我們自定義的對象也包含nodeType屬性呢？如
代碼如下:
var obj = {nodeType:1};
function isHTMLElement(obj){
if(obj.nodeType){
return obj.nodeType==1;
}
}
isHTMLElement(obj);//true

以上isHTMLElement(obj)返回true，但obj明顯不是一個HTML節點元素。下面通過對象特性及try-catch語句來判斷。
代碼如下:
function isHTMLElement(obj){
var d = document.createElement("div");
try{
d.appendChild(obj.cloneNode(true));
return obj.nodeType==1?true:false;
}catch(e){
return false;
}
}
var obj1 = {nodeType:1};
var obj2 = document.createTextNode("hello");
var obj2 = document.createElement("p");
isHTMLElement(obj1);//false
isHTMLElement(obj2);//false
isHTMLElement(obj3);//true

對于window和document還要特別處理下
代碼如下:
function isHtmlControl(obj) {

var d = document.createElement("div");
try{
d.appendChild(obj.cloneNode(true));
return obj.nodeType==1 ? true : false;
}catch(e){
return obj==window || obj==document;
}
}

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