assigning results of $.post to a variable

Hi,

I'm trying to put the result of a $.post request into a variable.
I've tried a few different ways, and none seem to work.  I've tried
working with the xmlhttprequest object that $.post returns:

function mytest()
{
        var mydate = new XMLHttpRequest();
        mydate = $.post("/calendar/calendarajax.php", {mycommand:
"geteventdates", month: ym}, function(data){
                        assigndays(data);
                        }, "text");
        alert("mydate is " + mydate.responseText);
//all that assigndays does is alert(data) just to make sure I have real data.
}
If I just do alert(mydate) the alert box does at least show that
mydate is an XMLHttpRequest object, I just can't seem to get its
responseText.
I've tried:
function mytest()
{
        var mydate;
         $.post("/calendar/calendarajax.php", {mycommand: "geteventdates",
month: ym}, function(data){
                        mydate = data;
                        }, "text");
        alert("mydate is " + mydate);
}

and
<script>
var mydate;
function mytest()
{

         $.post("/calendar/calendarajax.php", {mycommand: "geteventdates",
month: ym}, function(data){
                        mydate = data;
                        }, "text");
        alert("mydate is " + mydate);
}
</script>

In theory, because I've scoped mydate using var, the mydate inside the
function should refer to the mydate that was locally scoped to mytest
or it should use the global variable in the second example.

Any ideas on where I'm messing up?

Thanks,

Bob

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[Steven Black-2]

Hi Bob,

The problem here is synchronicity.  The post fires, but the mainline
javascript isn't waiting for the $.post to return before continuing.

THEREFORE, if you want sonething to happen post-$.post, use a
callback.

**--**  Steve

On Nov 9, 12:42 pm, Bob Ramsey <alfrod...@...> wrote:

> Hi,
>
> I'm trying to put the result of a $.post request into a variable.
> I've tried a few different ways, and none seem to work.  I've tried
> working with the xmlhttprequest object that $.post returns:
>
> function mytest()
> {
>         var mydate = new XMLHttpRequest();
>         mydate = $.post("/calendar/calendarajax.php", {mycommand:
> "geteventdates", month: ym}, function(data){
>                         assigndays(data);
>                         }, "text");
>         alert("mydate is " + mydate.responseText);
> //all that assigndays does is alert(data) just to make sure I have real data.}
>
> If I just do alert(mydate) the alert box does at least show that
> mydate is an XMLHttpRequest object, I just can't seem to get its
> responseText.
> I've tried:
> function mytest()
> {
>         var mydate;
>          $.post("/calendar/calendarajax.php", {mycommand: "geteventdates",
> month: ym}, function(data){
>                         mydate = data;
>                         }, "text");
>         alert("mydate is " + mydate);
>
> }
>
> and
> <script>
> var mydate;
> function mytest()
> {
>
>          $.post("/calendar/calendarajax.php", {mycommand: "geteventdates",
> month: ym}, function(data){
>                         mydate = data;
>                         }, "text");
>         alert("mydate is " + mydate);}
>
> </script>
>
> In theory, because I've scoped mydate using var, the mydate inside the
> function should refer to the mydate that was locally scoped to mytest
> or it should use the global variable in the second example.
>
> Any ideas on where I'm messing up?
>
> Thanks,
>
> Bob

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[yanick-2]

On Nov 9, 12:42 pm, Bob Ramsey <alfrod...@...> wrote:
> Hi,
>
> I'm trying to put the result of a $.post request into a variable.
> I've tried a few different ways, and none seem to work.  I've tried
> working with the xmlhttprequest object that $.post returns:
>
> function mytest()
> {
>         var mydate = new XMLHttpRequest();

Why are you instanciating an XMLHttpRequest ??

>         mydate = $.post("/calendar/calendarajax.php", {mycommand:

You are discarding it right at the next line !! Moreover,
XMLHttpRequest is not a valid Javascript object in some browsers (see
http://en.wikipedia.org/wiki/XMLHttpRequest). But in any case, JQuery
does it for you so you don't have to take care of that.

> "geteventdates", month: ym}, function(data){
>                         assigndays(data);
>                         }, "text");
>         alert("mydate is " + mydate.responseText);
> //all that assigndays does is alert(data) just to make sure I have real data.}
>
> If I just do alert(mydate) the alert box does at least show that
> mydate is an XMLHttpRequest object, I just can't seem to get its
> responseText.
> I've tried:
> function mytest()
> {
>         var mydate;
>          $.post("/calendar/calendarajax.php", {mycommand: "geteventdates",
> month: ym}, function(data){
>                         mydate = data;
>                         }, "text");
>         alert("mydate is " + mydate);
>
> }
>
> and
> <script>
> var mydate;
> function mytest()
> {
>
>          $.post("/calendar/calendarajax.php", {mycommand: "geteventdates",
> month: ym}, function(data){
>                         mydate = data;
>                         }, "text");
>         alert("mydate is " + mydate);}
>
> </script>
>

Yes, but the alert prints out "mydate" before the request has even
been made! The order of things happening in this script is :

1.initiate a POST request to given url and with given params
2. alert "mydate is "+ mydate (will output "mydate is undefined" since
never assigned)
3. send request (most browser's javascript engine are single threaded,
so you couldn't send the request while still being executing
something)
[... after a few milliseconds...]
4. receiving a response
5. assigning it to mydate

Remember that, when playing with Ajax, generally, everything is or
should be asynchronous, meaning that the order of execution do or
should not happen in a procedural way.

 function mytest() {
    $.post("/calendar/calendarajax.php", {mycommand: "geteventdates",
month: ym}, function(data){
        var mydate = data;
        alert("mydate is " + mydate);

        // or set a DOMElement's text : $('selector').text("mydate is
" + mydate);
        // is a better alternative to debug things than an alert
box...
    }, "text");
}

It is not good practive to declare "var mydate;" globally or outside a
function scope. If you need the mydate variable somewhere else in your
code, you should, rather, store it somewhere else. Read jQuery.data
(http://docs.jquery.com/Internals/jQuery.data) to store raw data (used
usually for storing flags and element's states).

Hope this helps.

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