dynamic - checking dynamically named selects using jquery -

how can use jquery value of dynamically named select?

i have several (no exact number) of selects populated this:

<?php     ($i = 0; $i < count($manifest); $i++)         echo '<select id="headercolumn_' . $i . '">             <option value="">-- column header --</option>             <option value="1">option 1</option>             <option value="2">option 2</option>             <option value="3">option 3</option>             <option value="4">option 4</option>         </select>';     ?> 

later on, have button includes onclick function. when function called, pass how many selects created. now, need value of selects. tried this:

for (var = 0; < valuepassedintofunction; i++) {     var thisvalue = $("#headercolumn_" + i).val();     alert("#headercolumn_" + + " = " + thisvalue); } 

but when run page, popup this:

#headercolumn_1 = undefined 

how can jquery accept dynamic naming convention?

use $.map function iterate on elements id starting headercolumn_, , return each elements value array :

var arr = $.map($('[id^="headercolumn_"]'), function(el, i) {return el.value; }); 

or alert id's , values:

$('[id^="headercolumn_"]').each(function(i, el) {     alert(el.id + ' = ' + el.value); });