Ajax and IE6

[Vincent]

Hi all,

I've seen a lot of ajax examples on the web that used an event handler
called 'processChange' for the onreadystatecha nge event. Normally,
this looks like this:

if(window.XMLHt tpRequest) obj = new XMLHttpRequest( );
else if(window.Activ eXObject) obj = new
ActiveXObject(' Microsoft.XMLHT TP');

obj.onreadystat echange = processChange;
....

function processChange() {
if(obj.readysta te != 4) return;
if(obj.status == 200){
// do something
}
}

Well, this works on IE6 and Firefox, but I would like to use this
instead of obj inside of the processChange function (this.readystat e
and this.status). This works fine on firefox, but on IE6 it doesn't.
Can someone tell me why?

For the record, I want to use this instead of obj because I want to
make a series of request with a for loop and since happens all inside
of the same closure, obj would refer to the last instance of my
xmlhttprequest.

Thanks,

Vincent

[slebetman]

Re: Ajax and IE6

On Jul 22, 3:41 am, Vincent <vincentdeh...@ gmail.comwrote:

if(window.XMLHt tpRequest) obj = new XMLHttpRequest( );
else if(window.Activ eXObject) obj = new
ActiveXObject(' Microsoft.XMLHT TP');
>
obj.onreadystat echange = processChange;
...
>
function processChange() {
   if(obj.readysta te != 4) return;
   if(obj.status == 200){
   // do something
   }
>
}
<snip>
For the record, I want to use this instead of obj because I want to
make a series of request with a for loop and since happens all inside
of the same closure, obj would refer to the last instance of my
xmlhttprequest.
>

Rather than using 'this', which changes meaning depending on the
context where the code gets executed, there is another trick you can
use to avoid creating a closure: pass the value of obj instead of
using obj directly.

/* function generator allowing us to pass
* the xmlhttprequest object rather than
* create a closure:
*/
function makeProcessChan geHandler (ajaxObj) {
/* admittedly, it is still a closure
* only in a different scope
*/
return function () {
if(ajaxObj.read ystate != 4) return;
if(ajaxObj.stat us == 200){
// do something
}
}
}
obj.onreadystat echange = makeProcessChan geHandler(obj);

[Henry]

Re: Ajax and IE6

On Jul 22, 12:40 pm, slebetman wrote:
<snip>

... , there is another trick you can use to avoid
creating a closure: pass the value of obj instead of
using obj directly.
>
/* function generator allowing us to pass
* the xmlhttprequest object rather than
* create a closure:
*/
function makeProcessChan geHandler (ajaxObj) {
/* admittedly, it is still a closure
* only in a different scope
*/
return function () {
if(ajaxObj.read ystate != 4) return;
if(ajaxObj.stat us == 200){
// do something
}
}}
>
obj.onreadystat echange = makeProcessChan geHandler(obj);

That is creating a closure.

[Jorge]

Re: Ajax and IE6

On Jul 22, 1:40 pm, slebetman <slebet...@gmai l.comwrote:

>
Rather than using 'this', which changes meaning depending on the
context where the code gets executed, there is another trick you can
use to avoid creating a closure: pass the value of obj instead of
using obj directly.
>
/* function generator allowing us to pass
 * the xmlhttprequest object rather than
 * create a closure:
 */
function makeProcessChan geHandler (ajaxObj) {
  /* admittedly, it is still a closure
   * only in a different scope
   */
  return function () {
    if(ajaxObj.read ystate != 4) return;
    if(ajaxObj.stat us == 200){
    // do something
    }
  }}
>
obj.onreadystat echange = makeProcessChan geHandler(obj);

Yeah !
Other objects and data could be captured as needed in that same
closure as well :

xhr.onreadystat echange = (function (xhr, object, data) {
return function () {

//xhr, object, and data have been captured in the closure.

}
})(xhr, someOtherObject , i);


"auto-reposting, closurized, xhr monitor and exerciser"
http://tinyurl.com/6mm5tm :-)

--Jorge.

[Jorge]

Re: Ajax and IE6

On Jul 22, 5:40 pm, Jorge <jo...@jorgecha morro.comwrote:

>
"auto-reposting, closurized, xhr monitor and exerciser"

http://tinyurl.com/6mm5tm :-)

>

BTW, FF3 now seems to handle 6 simultaneous requests...
Safari, Opera: 4
FF2: 2
etc: 2

--Jorge.