Javascript XMLHttpRequest无法与IE 8或9一起发送，但可以与IE 10一起使用

Question

I am currently having a lot of troubles making ajax works with IE versions inferior to 10 while I have no problem with Firefox, Chrome, Safari, Opera and even IE 10. My website just shows 3 select menus linked together, 2 of which get filled with data coming from a mysql database whenever something is selected in the first one and then in the second one. Apache logs don't show any POST request being done when using IE 8 or 9 and my select menus won't get filled with data.

This is my javascript code:

function getXMLHttpRequest() {

   var xhr = null;

   if (window.XMLHttpRequest || window.ActiveXObject) {
      if (window.ActiveXObject) {
         try {
            xhr = new ActiveXObject("Msxml2.XMLHTTP");
         } catch(e) {
            xhr = new ActiveXObject("Microsoft.XMLHTTP");
         }
      } else {
         xhr = new XMLHttpRequest();
      }
   } else {
      alert("Your browser doesn't support XMLHTTPRequest...");
      return null;
   }

   return xhr;

}

function request(oSelect) {

   var value = oSelect.options[oSelect.selectedIndex].value;

   var xhr = getXMLHttpRequest();

   xhr.onreadystatechange = function() {
      if(xhr.readyState == 4 && (xhr.status == 200 || xhr.status == 0)) {
         displayOptions(xhr.responseText, oSelect);
      }
   }

   xhr.open("POST", "ajax.pl", true);
   xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
   xhr.send(oSelect.name + "=" + value);

}

function displayOptions(oData, oSelect) {

   if (oSelect.name == "genus") {
      document.getElementsByName("species")[0].disabled = false;
      document.getElementsByName("species")[0].innerHTML = oData;
      document.getElementsByName("subspecies")[0].disabled = true;
      document.getElementsByName("subspecies")[0].innerHTML = "";
   }
   if (oSelect.name == "species") {
      document.getElementsByName("subspecies")[0].disabled = false;
      document.getElementsByName("subspecies")[0].innerHTML = oData;
   }

}

So far I have tried to change the xhr.open command from POST to GET, but without any luck. I also tried to put the absolute path to the perl cgi in the xhr.send command, but without any effect on IE 8 at all.

I have also tried the following thing:

xhr.onreadystatechange = function() {
   if(xhr.readyState == 0) {
      alert("zero");
   }
   if(xhr.readyState == 1) {
      alert("one");
   }
   if(xhr.readyState == 2) {
      alert("two");
   }
   if(xhr.readyState == 3) {
      alert("three");
   }
   if(xhr.readyState == 4 && (xhr.status == 200 || xhr.status == 0)) {
      alert("four");
      displayOptions(xhr.responseText, oSelect);
   }
}

This gives me the following output with Chrome:

one
two
three
four

While I have this one with IE 8:

one
one
four

Since I'm a newbie I fail to find what could cause this problem. I've been wandering the web for answers but still haven't found one.

Any would then be much much appreciated as I start to be desperate.

Answer 1

I found a workaround by using jQuery as Oscar suggested.

Here is the code I wrote that replaced the js functions in my above post, it works like a charm:

$(document).ready(function() {

var $genus = $('#genus');
var $species = $('#species');
var $subspecies = $('#subspecies');

$genus.on('change', function() {

    var value = $(this).val();

    $species.empty();
    $subspecies.empty();

    if(value != '') {
        $species.removeAttr('disabled');
        $subspecies.attr('disabled', 'disabled');

        $.ajax({
            url: 'ajax.pl',
            data: 'genus=' + value,
            dataType: 'html',
            success: function(code_html) {
                $(code_html).appendTo('#species');
            }
        });
    } else {
        $species.attr('disabled', 'disabled');
        $subspecies.attr('disabled', 'disabled');
    }
});

$species.on('change', function() {

    var value = $(this).val();

    $subspecies.empty();

    if (value != '') {
        $subspecies.removeAttr('disabled');

        $.ajax({
            url: 'ajax.pl',
            data: 'species=' + value,
            dataType: 'html',
            success: function(code_html) {
                $(code_html).appendTo('#subspecies');
            }
        });
    } else {
        $subspecies.attr('disabled', 'disabled');
    }
});

});