I'm trying to wait for the AJAX request to plete. It would be easy if the method xmlhttp.open would support async = false but Ant Galio does not support this option and only asynchronous requests are permitted. The question is how can I wait for the callback to be called.

    var ajaxFinished = false;
    var xmlhttp = new XMLHttpRequest();
    this.debug("-- onreadystatechange is being defined");
    xmlhttp.onreadystatechange = function() {
        if (xmlhttp.readyState == 4) {
            ajaxFinished = true;
                var data = xmlhttp.responseText;
            if (xmlhttp.status == 200) {
                that.debug('downloadSettings: SUCCESS');
                [...]
            } else {
                that.debug('downloadSettings:');
                that.debug('-- Error: ');
                that.debug('-- ResponseText: "'+data+'"')
            }
        }
    }

    while (ajaxFinished == false) {

    }

    this.debug("-- open connection");
    xmlhttp.open("GET", requestUrl, true); /* Ant Galio does not support synchronous  */
    this.debug("-- send");
    xmlhttp.send();                 

I'm looking for some kind of active waiting. I know about another solution but I'm interested in a solution that would not require changing more of the code than is my example above.

Thanks!

I'm trying to wait for the AJAX request to plete. It would be easy if the method xmlhttp.open would support async = false but Ant Galio does not support this option and only asynchronous requests are permitted. The question is how can I wait for the callback to be called.

    var ajaxFinished = false;
    var xmlhttp = new XMLHttpRequest();
    this.debug("-- onreadystatechange is being defined");
    xmlhttp.onreadystatechange = function() {
        if (xmlhttp.readyState == 4) {
            ajaxFinished = true;
                var data = xmlhttp.responseText;
            if (xmlhttp.status == 200) {
                that.debug('downloadSettings: SUCCESS');
                [...]
            } else {
                that.debug('downloadSettings:');
                that.debug('-- Error: ');
                that.debug('-- ResponseText: "'+data+'"')
            }
        }
    }

    while (ajaxFinished == false) {

    }

    this.debug("-- open connection");
    xmlhttp.open("GET", requestUrl, true); /* Ant Galio does not support synchronous  */
    this.debug("-- send");
    xmlhttp.send();                 

I'm looking for some kind of active waiting. I know about another solution but I'm interested in a solution that would not require changing more of the code than is my example above.

Thanks!

• javascript
• ajax

3 Answers 3

yes, you can

function getFile(url) {
  if (window.XMLHttpRequest) {              
    AJAX=new XMLHttpRequest();              
  } else {                                  
    AJAX=new ActiveXObject("Microsoft.XMLHTTP");
  }
  if (AJAX) {
     AJAX.open("GET", url, false);                             
     AJAX.send(null);
     return AJAX.responseText;                                         
  } else {
     return false;
  }                                             
}

var fileFromServer = getFile('http://somedomain./somefile.txt');

w3c definition http://www.w3/TR/XMLHttpRequest/#the-open()-method

client . open(method, url [, async = true [, user = null [, password = null]]])

You can't. There is no "active waiting" in JavaScript, there can be only one active execution a time ("single-threaded").

There is a workaround. Instead of using the the blocking while loop for poll use the nonblocking setInterval().. so your code might look something like this.

 


    var ajaxFinished = false; 
    var xmlhttp = new XMLHttpRequest(); 
    this.debug("-- onreadystatechange is being defined"); 
    xmlhttp.onreadystatechange = function() { 
     if (xmlhttp.readyState == 4) { 
      ajaxFinished = true; 
      var data = xmlhttp.responseText; 
      if (xmlhttp.status == 200) { 
        that.debug('downloadSettings: SUCCESS'); 
         [...] 
      } else { 
         that.debug('downloadSettings:'); 
         that.debug('-- Error: "); 
         that.debug('-- ResponseText: "'+data+'"') 
      } 
     } 
    } 

    //Polling function 

    function checkEvent(){
    if(ajaxFinished == true){
    //your code i.e xmlhttp.open("GET", requestUrl, true);
    }
    clearInterval(chkeventid);//Clear Interval via ID for single time execution
    }

    var chkeventid=self.setInterval("checkEvent()",100);//The poll call

    The setInterval method is treated a bit differently in JS as you know so you may use it as against the while loop.