TypeError：無法讀取未定義的屬性“open”（Phonegap和Ionic）

Question

我正在使用Phonegap Build和Ionic構建移動應用程序。 我正在嘗試為Web服務創建XMLHttpRequest以獲取一些XML數據。 Web服務需要3個參數。 我一直收到以下錯誤：

ionic.bundle.js：26794 TypeError：無法讀取undefined屬性'open'。

關於我可能做錯什么的任何想法？

我已經附上了下面的整個方法。

$scope.result = function callService(requestAction, requestXML){

  var httpObj = undefined; 

  if(window.XMLHttpRequest){    
    httpObj = new XMLHttpRequest();    
  }    
  else if (window.ActiveXObject){    
    httpObj = new ActiveXObject("Microsoft.XMLHTTP"); 
  }

  if(httpObj = undefined){
    alert("Failed creating Http Object");     
    return ""; 
  }

  if(requestAction == undefined || requestAction == null){
    requestAction = "";    
  }

  var async = false; 
  var url = "theurl";     
  var systemID = "thesystemid";     
  var requestAction = "GetEnquiry"; 
  var requestXML = "therequestxml"; 
  var params = "SystemID=" + systemID + "&RequestAction=" + requestAction + "&RequestXML=" + requestXML + "&OutputFormat=JSON";            
  var headers = "Content-type , application/x-www-form-urlencoded; charset=UTF-8"; 

  httpObj.open("POST", url, async);                 
  httpObj.send(params);

  if(httpObj.readyState == 4 && httpObj.status == 200){
    var result = httpObj.responseText; 
    console.log("This is the result: " + result);    
    return result; 
  }    
  else {    
    var result = httpObj.responseText;     
    return result; 
  }   
};   
})

Answer 1

問題是httpObj對象未定義，您嘗試訪問undefined的方法。 您沒有在警報中定義錯誤消息（當httpObj undefined ）的原因是您的條件不正確。 這個

if(httpObj = undefined){

應該像下面這樣：

if(httpObj === undefined){

或者等同於：

if(httObj){