post value still retains the same value after assigning it using $.post - forms

Question

<script type="text/javascript">
$(document).ready(function($) {
$('#searchicon').click(function(){
$('#searchicon.toappear').toggle();
$('#searchicon2.appear').toggle();
$('#extraSearch').slideToggle('fast');
});
$('#searchicon2').click(function(){
$('#searchicon.toappear').toggle();
$('#searchicon2.appear').toggle();
$('#extraSearch').slideToggle('fast');
});
$('input[name=estimate]').click(function(){
if (this.checked) {
$("input.groupestimate").removeAttr("disabled");
} else {
$("input.groupestimate").attr("checked", false);
$("input.groupestimate").attr("disabled", true);
}
});
$("input.groupgatepass").attr("disabled", true);
$('input[name=gatepass]').click(function(){
if (this.checked) {
$("input.groupgatepass").removeAttr("disabled");
} else {
$("input.groupgatepass").attr("checked", false);
$("input.groupgatepass").attr("disabled", true);
}
});
/*
$('input.groupestimate').click(function() {
if(this.checked) {
$form = $('#globalSearch form');
if($('#globalSearch form[ACTION*="'+this.value+'"]'))
var data = new Object();
data.field = this.value;
var dataString = $.toJSON(data);
$.post('json.php',
{data: dataString},
function(res){
var obj = $.evalJSON(res);
$form.attr('ACTION',$form.attr('action')+''+obj.query);
}
);
}
});*/
$('#globalSearch form').submit(function() {
if($('input.groupheader[type=checkbox]:checked').length > 1) {
alert('Please check only Estimate or Gatepass');
return false;
}
var data = new Object();
$('input.groupheader[type=checkbox]:checked').each(function(){
data.header = this.value;
});
data.fields = new Array();
$header = 'input.group'+data.header;
$($header+'[type=checkbox]:checked').each(function(){
data.fields.push(this.value);
});
var dataString = $.toJSON(data);
$.post('json.php',
{data: dataString},
function(res){
var obj = $.evalJSON(res);
$('input[name=query]').val(obj.query);
}
);
alert($('input[name=query]').val()); //alerts nothing or the old value :(
return false;
});
});
</script>
-------------HTML PART-------------------
<form action="?<?php echo http_build_query(cloneGet(array("server-page"=>$GLOBALS["setting"]["current_folder"], "currpage"=>"0","OrderBy"=>"","ByDirect"=>"","search_flg"=>"-1")));?>" method="post" id="" name="">
<div id="extraSearch">
<table class="stripe" width="100%" id="extraTableList">
<tbody>
<tr class="striped">
<th style="cursor:pointer;text-align:left;"><input type="checkbox" name="estimate" value="estimate" checked="checked" class="groupheader">Estimates</th>
<th style="cursor:pointer;text-align:left;"><input type="checkbox" name="gatepass" value="gatepass" class="groupheader">Gatepass</th>
</tr>
<tr>
<td class="int"><input type="checkbox" name="estimate1" value="customer" class="groupestimate">Customer</td>
<td class="int"><input type="checkbox" name="gatepass1" value="old_serial" class="groupgatepass">Old Serial</td>
</tr>
<tr>
<td class="int"><input type="checkbox" name="estimate2" value="serial_no" class="groupestimate">Serial No</td>
<td class="int"><input type="checkbox" name="gatepass2" value="type" class="groupgatepass">Type</td>
</tr>
<tr>
<td class="int"><input type="checkbox" name="estimate3" value="invoice_no" class="groupestimate">Invoice No</td>
<td class="int"><input type="checkbox" name="gatepass3" value="type_id" class="groupgatepass">Type ID</td>
</tr>
<tr>
<td class="int"><input type="checkbox" name="estimate4" value="salesman" class="groupestimate">Salesman</td>
<td class="int"><input type="checkbox" name="gatepass4" value="loader" class="groupgatepass">Loader</td>
</tr>
<tr>
<td class="int"><input type="checkbox" name="estimate5" value="estimate_no" class="groupestimate">Estimate No</td>
<td class="int"><input type="checkbox" name="gatepass5" value="total" class="groupgatepass">Total</td>
</tr>
<tr>
<td class="int"><input type="checkbox" name="estimate6" value="status" class="groupestimate">Status</td>
<td class="int"> </td>
</tr>
</tbody>
</table>
</div>
<img id="searchicon" src="___images/search-arrow.png" class="toappear" alt="Extra search" title="Extra search"/>
<img id="searchicon2" src="___images/search-arrow.png" class="appear" alt="Extra search" title="Extra search"/>
<input type="text" value="<?php echo $_REQUEST['quicksearch'];?>" id="s" name="quicksearch">
<input type="hidden" value="" id="query" name="query" temp="">
<input type="submit" value="Search" id="b">
<?php if( $_REQUEST['quicksearch'] ) { ?>
<a id="c" href="?<?php echo http_build_query(cloneGet(array("quicksearch"=>"","search_flg"=>"-1")));?>">Cancel</a>
<?php } ?>
</form>
As you can see, before it submits the values I want to insert a string into the 'query' input element value attribute. It works perfectly when doing it inside the callback of $.post but after checking it using alert() outside the $.post its empty.
Is $.post always like that?or am I missing something?

Answer 1

when you are using $.post it is making an async request. The reason alert will contain nothing or the old value is because it is triggered before the $.post can complete its request. When the alert is placed inside of the $.post callback it will have the data you want because it is called after the $.post has completed