I'm trying to fetch some content from another source using XHR as shown below:
function fetchPage(str)
{
if(str=="")
{
document.getElementById("table").innerHTML="";
resetFilters();
$('#progress').hide(); //fetching progress bar <div>
return;
}
if (window.XMLHttpRequest) // code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
else // code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
xmlhttp.onreadystatechange=postCallback;
xmlhttp.open("GET", "fetch.php?url=http://www.sis.itu.edu.tr/tr/ders_programlari/LSprogramlar/prg.php?fb="+str, true);
xmlhttp.send();
// any stuff that goes here will happen before callback
// (this is a good place to update a UI element showing a call is resolving.)
// (for example a spinner or text saying "fetching")
$('#progress').show();
progressFetching();
switch(xmlhttp.readyState){ //loading bar adjustments
case 0:
$('.bar').css("width","0%");
$('.bar').text("0%");
break;
case 1:
$('.bar').css("width","25%");
$('.bar').text("25%");
break;
case 2:
$('.bar').css("width","50%");
$('.bar').text("50%");
break;
case 3:
$('.bar').css("width","75%");
$('.bar').text("75%");
break;
}
}
function postCallback()
{
if (xmlhttp.readyState==4 && xmlhttp.status==200){
progressDone(); //loading is finished
$('#error').hide();
document.getElementById("table").innerHTML=xmlhttp.responseText;
// continue to process post callback.
resetFilters();
}
else {
// report error with fetch
/*if(xmlhttp.status==404 || xmlhttp.responseText == "")
$('#error').show();*/
//$('#error').show();
}
}
I want my page to display error when connection timeout occurs, or when the computer doesn't have an internet connection (maybe a disconnection occurred while hanging around) or any other situation where the webpage fails to fetch the contents of the other source.
Using the code above, in the else
block, if I go for if(xmlhttp.status==404 || xmlhttp.responseText == "")
in the /* */
comment section, I won't get an error unless its not a 404 error. If i go for //
comment section, error will be displayed after the fetching process is started until it is completed, i.e. between xmlhttp.readyState = 0
through xmlhttp.readyState = 4
. How can I display connection error messages using these attributes or something else?
Thank your for your attention:)
The problem is my template in prior question was flawed. I believe this will work better because it creates a closure to pass the variable you need to work with.
Once again, I did not test this so it might have typos and bugs -- nor did I change anything except how postCallback()
is invoked and added a parameter to it.
function fetchPage(str)
{
if(str=="")
{
document.getElementById("table").innerHTML="";
resetFilters();
$('#progress').hide(); //fetching progress bar <div>
return;
}
var xmlhttp;
if (window.XMLHttpRequest) // code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
else // code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
xmlhttp.onreadystatechange=function () { postCallback(xmlhttp); };
xmlhttp.open("GET", "fetch.php?url=http://www.sis.itu.edu.tr/tr/ders_programlari/LSprogramlar/prg.php?fb="+str, true);
xmlhttp.send();
// any stuff that goes here will happen before callback
// (this is a good place to update a UI element showing a call is resolving.)
// (for example a spinner or text saying "fetching")
$('#progress').show();
progressFetching();
switch(xmlhttp.readyState){ //loading bar adjustments
case 0:
$('.bar').css("width","0%");
$('.bar').text("0%");
break;
case 1:
$('.bar').css("width","25%");
$('.bar').text("25%");
break;
case 2:
$('.bar').css("width","50%");
$('.bar').text("50%");
break;
case 3:
$('.bar').css("width","75%");
$('.bar').text("75%");
break;
}
}
function postCallback(xmlhttp)
{
if (xmlhttp.readyState==4 && xmlhttp.status==200){
progressDone(); //loading is finished
$('#error').hide();
document.getElementById("table").innerHTML=xmlhttp.responseText;
// continue to process post callback.
resetFilters();
}
else {
// report error with fetch
/*if(xmlhttp.status==404 || xmlhttp.responseText == "")
$('#error').show();*/
//$('#error').show();
}
}