Javascript select / deselect

Javascript code
function checkAll()
{
var field = document.getElementsByName('list[]');
for (i = 0; i < field.length; i++)
field[i].checked = true ;
}

function uncheckAll()
{
var field = document.getElementsByName('list[]');
for (i = 0; i < field.length; i++)
field[i].checked = false ;
}



PHP Code :
if ( isset($_POST['submit']) ) {
//print_r($_POST['list']);
$postCount = count($_POST['list']);

for ( $i=0; $i < $postCount; $i++ ) {

//$deleteIds .= $_POST['list'][$i].',';
echo $_POST['list'][$i]."
";

}
}