同一域xmlhttprequest访问被拒绝，即ie8

Question

I'm fairly new to the world of web development and am trying to read a txt file in internet explorer 8 and compare it to source code of a website to see if they are equal. This is so I can work out if the web page is functioning correctly.

I managed to get the source code with an xmlhttprequest and have tried the same to get the text file (which is in the same domain as my web page) and I am getting an access denied error.

After some research I can see that cross-domain xmlhttprequests won't work but that's not what I'm trying to do so I'm not sure how to proceed.

Having run the same code in Firefox(current version). It will read the file but not the web page!

I don't mind which of the two browsers I end up using but at the moment each does half of what I want it to.

my code is:

function source1(){
    xmlhttp=new XMLHttpRequest();
    xmlhttp.open("GET", "http://website",true);
    xmlhttp.onreadystatechange=function() {
        if (xmlhttp.readyState==4) {
            document.getElementById('textzone').value = xmlhttp.responseText
            var inputString = xmlhttp.responseText;
            alert(inputString);
            comparison(inputString)
        }
    }
    xmlhttp.send(null)
}

function comparison(inputString){
    xmlhttp1=new XMLHttpRequest();
    xmlhttp1.open("GET", "comparisondoc.txt", false);
    xmlhttp1.onreadystatechange=function() {
        if (xmlhttp1.readyState==4) {
            var compareString = xmlhttp1.responseText;
            alert(compareString)
            if(inputString==compareString){
                alert("Strings are equal");
            }
        }
    }
    xmlhttp.send(null)
}

All I need to know is why either the file won't open in ie8, or why the website source code shows up blank (in the alert) in firefox. Any help would be appreciated.

Answer 1

It could be a browser support issue. Try the following code to initialize your XMLHttpRequest :

function createRequest() {
  try {
    request = new XMLHttpRequest();
  } catch (trymicrosoft) {
    try {
      request = new ActiveXObject("Msxml2.XMLHTTP");
    } catch (othermicrosoft) {
      try {
        request = new ActiveXObject("Microsoft.XMLHTTP");
      } catch (failed) {
        request = false;
      }
    }
  }

  if (!request)
    alert("Error initializing XMLHttpRequest!");
}

Answer 2

Check your comparison function. You should you xmlhttp1 instead of xmlhttp at 2 places

function comparison(inputString){
    xmlhttp1=new XMLHttpRequest();
    xmlhttp1.open("GET", "comparisondoc.txt", false);
    xmlhttp1.onreadystatechange=function() {
        if (xmlhttp1.readyState==4) {
            <!--alert(xmlhttp1.responseText)-->
            var compareString = xmlhttp1.responseText;
            alert(compareString)
            if(inputString==compareString){
                alert("Strings are equal");
            }
        }
    }
    xmlhttp1.send(null)
}

Answer 3

Try to add the if(xmlhttp.status == 200) { } stuff. Remember both of these are looping through status' "AND" readystates.

Technically you could be erroring somewhere (I'd rather not speculate on) halting progress to next request or whatever without the status check.

Also you "should" try other request techniques. ie.. xmlhttp.onreadystatechange = function(){itsReady(inputString)}; // we keep this line short and simple calling to another func that contains your status and readystate checks, response stuff, and more func.

On a pretty normal run the Loop looks like: hi rdySte:1///status 0//////// hi rdySte:2///status 200//////// hi rdySte:3///status 200//////// hi rdySte:4///status 200////////

I ran into a lot of weird issues trying the long onreadystatechange = function (){ ... All stuff..} I successfully run a crazy set of request functionalities using the short onreadystatechange technique.

I noticed at the last minute-> is there a reason why the async flags are different between your funcs? I'd set them all to true unless you have a great reason.

This will work: ( to test: 2 pages t1.php contains a num or whatever and t2.txt that has a num in sam dir as the funcs are called in )

function source1(){
                                            var avar = 1;
                                                xmlhttp=new XMLHttpRequest();
                                                xmlhttp.open("GET", "t1.php",true); // shortened f-names for ease of test
                                                xmlhttp.onreadystatechange = function(){jsg_snd(avar)};
                                                xmlhttp.send(null)
}

function jsg_snd(avar){
    if (xmlhttp.readyState==4) {
        if (xmlhttp.status == 200) {
                                            var inputString = xmlhttp.responseText;
                                                document.getElementById('text_zone').innerHTML = inputString;
                                                document.getElementById('text_zone1').value = inputString;
                                                // alert(inputString);//
                                                comparison(inputString)
        }
    }
}

function comparison(inputString){
        xmlhttp1=new XMLHttpRequest();
                                                xmlhttp1.open("GET", "t2.txt", true);
                                                xmlhttp1.onreadystatechange= function(){jsg_snd1(inputString);};
                                                xmlhttp1.send(null)
}

function jsg_snd1(inputString){
    if (xmlhttp1.readyState==4) {
        if (xmlhttp1.status == 200) {
                                            var compareString = xmlhttp1.responseText;
                                                        //alert(compareString)
            if(inputString==compareString){
                                                        //alert("Strings are equal");
                                                document.getElementById('text_zone').innerHTML += "; Ok "+inputString+"=="+compareString+"";
            }
        }
    }
}

Now the html in your body should look like:

    <tt id = 'text_go' onMouseUp="source1();" >Go!</tt>
    <tt id = 'text_zone' onMouseUp="text_zone.innerHTML = '';" >Click to clear!</tt>
    <input type ='text' id = 'text_zone1' onMouseUp="text_zone1.value = '';" value = 'Click to clear!' >

The extra stuf is for _ __s & giggles.