JS

Question

请参阅以下代码：

function createXMLHttpRequestObject() {
    // will store the reference to the XMLHttpRequest object
    var ajaxRequest;
    // create the XMLHttpRequest object
    try{
        // Opera 8.0+, Firefox, Safari
        ajaxRequest = new XMLHttpRequest();
    } catch (e){
        // Internet Explorer Browsers
        try{
            ajaxRequest = new ActiveXObject("Msxml2.XMLHTTP");
        } catch (e) {
            try{
                ajaxRequest = new ActiveXObject("Microsoft.XMLHTTP");
            } catch (e){
                // Something went wrong
                alert("Your browser broke!");
                return false;
            }
        }
    }
    // return the created object or display an error message
    if (!ajaxRequest) alert("Error creating the XMLHttpRequest object.");
    else return ajaxRequest;
}


function ajax_update() {
  var ajaxRequest = createXMLHttpRequestObject();

  ajaxRequest.onreadystatechange = function(){

    if(ajaxRequest.readyState != 4){ 
    ...
    }

    if(ajaxRequest.readyState == 4){
    //process JSON data
    }
  }
}

我正在尝试从ajax_update（）函数外部监视/侦听ajaxRequest.readyState值。按钮onlick上会触发ajax_update（）。

我的目标是在函数ajax_update（）之外仅在所有Ajax调用完成时触发另一个JS函数，这意味着ajaxRequest.readyState == 4.

代表：

 <input type='button' value='SEND QUOTE' onclick=\"ajax_update(some params); function_that_fires_when_readystate_is_completed();\">

有什么想法吗？

提前谢谢！

Answer 1

定义这个全局

 var requestCounter = 0;

然后

function ajax_update() {
  var ajaxRequest = createXMLHttpRequestObject();
  //after calling request.open();
    requestCounter++;

  ajaxRequest.onreadystatechange = function(){  

    if(ajaxRequest.readyState != 4){ 
          requestCounter--;
          //error code here
    }

    if(ajaxRequest.readyState == 4){
        //process JSON data
          requestCounter--;
    }

     if (requestCounter == 0)
          onAllRequestComplete();
  }
}


     function onAllRequestComplete(){
        // code that have to run when all requests have been completed
     }

希望有所帮助。

Answer 2

使用回调。

JS

function ajax_update(callback) {
  var ajaxRequest = createXMLHttpRequestObject();
  ajaxRequest.onreadystatechange = function(){
    if(ajaxRequest.readyState == 4){
      callback();
    }
  };
  xmlhttp.open(...);
  xmlhttp.send(null);
}

HTML

<input onclick="ajax_update(function_that_listens_to_readyState);">

Answer 3

ajaxRequest1.onreadystatechange = function(){

    if(ajaxRequest.readyState != 4){ 
    ...
    }

    if(ajaxRequest.readyState == 4){
    //process JSON data
       firstIsReady  = true;
       check();
    }
  }

ajaxRequest2.onreadystatechange = function(){

    if(ajaxRequest.readyState != 4){ 
    ...
    }

    if(ajaxRequest.readyState == 4){
    //process JSON data
       secondIsReady  = true;
       check();
    }
  }

function check() {
    if (firstIsReady && secondIsReady) {
        //both ajax calls completed
    }
}

这样的事情。这真的很难看，但如果不知道你想做什么，我就无法给你一个更好的方法。

监视/侦听Ajax readyState

3 个答案:

JS

HTML