我們經常使用nodeType==1判斷元素是否是一個HMTLElement元素。頁面上的元素都是節點(Node)，有元素節點(Element Node)、屬性節點(Attribute Node)、文本節點(Text Node)等。w3c nodeType 的定義如下

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

復制代碼 代碼如下:

var obj = {nodeType:1};
function isHTMLElement(obj){
    if(obj.nodeType){
        return obj.nodeType==1;
    }
}
isHTMLElement(obj);//true

復制代碼 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

復制代碼 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;
    }
}